Term
|
Definition
| Cells that are capable of maintaining, generating and replacing terminally differentiated cells within their own specific tissue following normal cell turnover or in response to injury. Adult stem cells are now considered to have the capacity to differentiate beyond their own tissure boundaries; this capacity is called plasticity. |
|
|
Term
| Allele Specific Oligonucleotides (ASOs) |
|
Definition
| Oligonucleotides that are constructed with DNA sequences homologous to specific alleles. Two ASOs can be made which differ in sequence at only one nucleotide base, thereby distinguishing a mutant allele with a point mutation from its corresponding wild-type allele. |
|
|
Term
|
Definition
| Alternative forms of the same genes |
|
|
Term
|
Definition
| From one person to another who is genetically dissimilar but of the same species |
|
|
Term
|
Definition
| The most common interspersed repeat (~300bp in size) in human DNA, accounting for about 5% of the total DNA. So named because its cleaved by the restriction enzyme Alu |
|
|
Term
|
Definition
| The building blocks of proteins. Each amino acid is encoded by a nucleotide triplet (codon) |
|
|
Term
|
Definition
| Aspiration of amniotic fluid during pregnancy |
|
|
Term
|
Definition
| Multiple copies of a DNA sequence |
|
|
Term
|
Definition
| Any chromosome number that is not an exact multiple of the haploid number (23 in humans). Examples of aneuploidy include the presence of an extra copy of a single chromosome - e.g. trisomy 21 (Down's syndrome) - or the absence of a single chromosome - e.g. monosomy, as found in Tumer syndrome 45,X |
|
|
Term
|
Definition
| To form double-stranded nucleic acid from single stranded forms |
|
|
Term
| Annotation of DNA sequence/gene |
|
Definition
| The conversion of raw sequence data to knowledge of gene location on a chromosome and the function of that gene, i.e., characterisation of a gene. |
|
|
Term
|
Definition
| A protein produced by higher vertebrated following exposure to a foreign substance - antigen. The Y-shaped antibodies bind to antigens and neutralise them. Antibodies can be polyclonal or monoclonal in origin (the latter is derived from a single cell, and so each antibody is identical). More correct term is immunoglobin. |
|
|
Term
|
Definition
| Increasing severity or earlier age at onset of a genetic disease in successive generations. |
|
|
Term
|
Definition
| A more subtle form of variation than antigenic shift. Involves accumulation of mutations in the haemagglutinin and neuraminidase genes in the influenza A and B viruses. This reduces the effectiveness of previously acquired antibodies to influenza and so facilitates the spread of the virus |
|
|
Term
|
Definition
| A mechanism seen only with influenzae A viruses to escape the human immune response. It results from the replacement of haemagglutinin or the neuraminidase with novel subtypes that have not been around in humans for some time. These subtypes come from waterfowl, a large reservoir of influenzae viruses. The consequence is a pandemic, i.e. worldwide epidemic. |
|
|
Term
|
Definition
| Antisense DNA is the non-coding strand of DNA. The latter functions as the template for mRNA production, which then contains the sequence present on the sense strand. Antisense RNA or antisense oligonucleotides have sequences that are complementary to mRNA and so interfere with the latter's function. |
|
|
Term
|
Definition
A process involving programmed cell death.
It has also been called genetically determined cell
suicide. Leads to death of cells during development or
cell turnover in the adult. Mutations in genes involved in
apoptosis are associated with prolonged cell survival
including cancer. |
|
|
Term
|
Definition
Sexual reproduction in which the
pairing of mates is not random, i.e., members of a particular
group that are more (less) likely to mate with other
members of that group produce positive (negative)
assortive mating. |
|
|
Term
|
Definition
A virus that has become less pathogenic
following passage outside its natural host. |
|
|
Term
|
Definition
|
|
Term
|
Definition
Disease that is the result of an
abnormality affecting the 22 pairs of autosomes (non-sex
chromosomes). |
|
|
Term
|
Definition
| A virus that infects bacteria |
|
|
Term
|
Definition
A measurement of length for DNA. Includes
a nucleotide base with its complementary base; i.e.,
adenine (A) would bind to thymine (T) or cytosine (C) to
guanine (G) |
|
|
Term
|
Definition
The application of tools involving computation
and analysis to capture, store and interpret biological
data |
|
|
Term
|
Definition
A gene that would be a good starter to
initiate a search for the genetic basis of an inherited disorder
of unknown origin, e.g., the myosin genes in
muscle disorders. |
|
|
Term
|
Definition
Post-transcriptional change to the 5¢ end of the
growing mRNA molecule in which a modified nucleotide
(4 methylguanosine) is added. Has a functional role since
it is recognised by ribosomes as the initiation signal for
protein synthesis. |
|
|
Term
|
Definition
Physical or chemical agent that induces
cancer. |
|
|
Term
|
Definition
An individual who is heterozygous for a mutant
allele that causes a genetic disorder in the homozygous
or hemizygous states. |
|
|
Term
|
Definition
The timed sequence of events occurring
in a eukaryotic cell between mitotic divisions. Divided
into M (mitotic), S (DNA synthetic), G1 and G2 (gap
or pause phases) and Go (resting phase). The times for
each component differ between cell lines |
|
|
Term
|
Definition
Distance between DNA loci as
determined on a genetic map. A distance of 1 cM indicates
two markers are inherited separately 1% of the
time. In terms of the physical map, 1 cM is very approximately
equal to 1Mb (Mb; see megabase). Name is
derived from TH Morgan |
|
|
Term
|
Definition
The heterochromatic constricted portion
of a chromosome where the chromatids are joined |
|
|
Term
|
Definition
An individual composed of a mixture of
genetically different cells. A chimaera is distinguished
from a mosaic on the basis that the cells in the former
are derived from different zygotes, e.g., transgenic mouse
formed by the embryonic stem cell approach |
|
|
Term
| Chorionic villus sampling or sample (CVS) |
|
Definition
Biopsy of
the chorion frondosum during pregnancy to obtain a
source of fetal tissue for prenatal diagnosis. |
|
|
Term
|
Definition
The complex of DNA and protein in which
the genetic material is packaged inside the cells of organisms
with nuclei (eukaryotes). |
|
|
Term
|
Definition
A region of a gene or nearby locus
that affects its function. Could include regions such
as the promoter or an enhancer |
|
|
Term
|
Definition
To clone DNA means to take a gene or part of a
gene and isolate it from the remainder of genomic DNA
and then produce genetically identical material. The
cloned DNA can be produced in unlimited amounts. The term cloning has wider ramifications
since it also applies to the genetic duplication of cells or
even whole organisms, including potentially a human.
One method that has been used to clone various animal
species is called somatic cell nuclear transfer. |
|
|
Term
|
Definition
Three adjacent nucleotide bases in DNA/RNA
that encode for an amino acid |
|
|
Term
| Comparative genomic hybridisation (CGH) |
|
Definition
Microarrays
used to look for genomic gains or losses particularly
in cancer |
|
|
Term
|
Definition
The specific binding between the
purine-pyrimidine base pairs of double-stranded nucleic
acid. Thus, adenine (purine) will covalently bind to
thymine (pyrimidine) and guanine (purine) to cytosine
(pyrimidine) in a 1-to-1 ratio |
|
|
Term
|
Definition
DNA that is synthesised
from an mRNA template. The enzyme required for this is
reverse transcriptase |
|
|
Term
|
Definition
An individual with two different
mutant alleles at a locus. |
|
|
Term
|
Definition
Both members of a twin pair demonstrating
the same phenotype or trait |
|
|
Term
|
Definition
Inbred strains that differ from one another
in a small chromosomal segment, cf., syngeneic
inbred strains that are identical except for sexual
differences |
|
|
Term
|
Definition
|
|
Term
|
Definition
The finding that a DNA sequence
is present in a wide range of phylogenetically distant
organisms suggests functional significance since it is
unlikely that during evolution a region of DNA would
have remained unaltered unless it had a specific and
important function; e.g., it is a gene. The ras proto-oncogene
illustrates this since it is conserved in organisms as
divergent as humans and yeast. |
|
|
Term
|
Definition
Cells that would be representative
of an organism; e.g., in DNA testing for loss of heterozygosity,
examples of constitutional cells which
would provide a baseline for the DNA polymorphisms
would be lymphocytes (if the cancer is non-haematological)
or fibroblasts which could be obtained from a skin
biopsy. |
|
|
Term
|
Definition
Genes that are expressed following
interaction between a promoter and RNA polymerase
without additional regulation. Also called housekeeping
genes since often expressed in all cells at low levels. In
contrast are inducible genes, e.g., metallothionein,
which expresses following exposure to some heavy
metals. |
|
|
Term
|
Definition
The person seeking or referred for genetic
counselling |
|
|
Term
|
Definition
Overlapping clone sets that represent a continuous
region of DNA. |
|
|
Term
| Contiguous gene syndromes |
|
Definition
A group of disorders associated
with malformation patterns, often with mental
retardation and growth abnormalities. The clinical heterogeneity
found in these disorders usually reflects the
involvement of a number of physically related but otherwise
distinct genes. |
|
|
Term
|
Definition
Regions of 1–2kb containing a high
density of hypomethylated cytosine residuals associated
with guanine. CpG islands are frequently found at the 5¢
end of genes |
|
|
Term
|
Definition
Families of interacting proteins involved in the
regulation of the cell cycle. So named because their
levels are cell-cycle dependent. |
|
|
Term
|
Definition
Proteins (but not antibodies) released by
some cells in response to contact with an antigen, e.g.,
interleukin-2 (IL2). Cytokines function as intracellular
mediators, e.g., generation of immune response seen
with IL2 |
|
|
Term
|
Definition
(Also called Microarray.) Ordered, highdensity
arrangements of nucleic acid spots. Each spot
represents a different DNA probe attached to an immobile
surface. Probes can be cDNA or oligonucleotides.
This technology allows the simultaneous measurement of
transcriptional activity for hundreds to tens of thousands
of genes (i.e., transcriptome) in any cell under any condition |
|
|
Term
|
Definition
Identifying the function of a gene from its
DNA sequence. |
|
|
Term
|
Definition
| Loss of a segment of DNA or chromosome |
|
|
Term
|
Definition
The chromosome number found in somatic
cells. In humans this will be 46, i.e., twice the number
present in the germ cells |
|
|
Term
|
Definition
Members of a twin pair not demonstrating
the same phenotype or trait |
|
|
Term
|
Definition
| Presence of two copies of a chromosome. In uniparental disomy, both copies of a chromosome come from the same parent (with no contribution from the other parent). |
|
|
Term
|
Definition
Twins (fraternal) produced from two
separate ova fertilised by different sperms |
|
|
Term
|
Definition
A genetic disorder is said to have dominant
inheritance if the mutant phenotype is produced when only one of the two normal (wild-type) alleles at a particular
locus is mutated |
|
|
Term
|
Definition
Inactivation of one of the two
tumour suppressor gene loci can produce what appears
to be a dominant effect if the mutant protein inhibits the
normal product from the remaining normal allele. |
|
|
Term
|
Definition
The use of a pulsed electric field to
introduce DNA into cells in culture. |
|
|
Term
| Embryonic stem cells (ES cells) |
|
Definition
In the embryo’s blastocyst
stage before implantation, the inner cell mass contains
all the cells that will make up the fetus. Some of
these cells are pluripotential because they will give rise
to all types of somatic cells as well as the germ cells.
When these pluripotential stem cells are grown in vitro,
they are called embryonic stem cells |
|
|
Term
|
Definition
DNA sequences with the following properties:
(1) They increase transcriptional activity. (2) They are
effective even if inverted in position. (3) They operate
over long distances. |
|
|
Term
|
Definition
A gene that encodes envelope protein of a
retrovirus |
|
|
Term
|
Definition
Heritable change in the pattern of gene
expression mediated by mechanisms other than changes
in the primary DNA sequence of the gene. The changes
can be inherited, for example, imprinting, but they do
not involve an alteration in genetic information. When
considering epigenetics in the post Human Genome
Project era, a more suitable term might be epigenomics |
|
|
Term
|
Definition
In gene therapy, refers to vectors that remain
free in the target cell without being taken up into the
host’s genome. |
|
|
Term
|
Definition
Non-condensed, light-appearing bands
following staining to produce G (Giemsa) banding of
chromosomes. More likely to contain transcriptionally
active DNA |
|
|
Term
|
Definition
Organisms ranging from yeast to humans
that have nucleated cells. |
|
|
Term
|
Definition
|
|
Term
|
Definition
That segment in a gene which codes for a
polypeptide and is represented in the mRNA. |
|
|
Term
| Expressed sequence tag (EST) |
|
Definition
A small DNA segment
that can be amplified by PCR. This segment functions as
a unique identifier for a region of the genome. |
|
|
Term
|
Definition
The severity of a phenotype. Variable
expressivity is a feature of autosomal dominant disorders. |
|
|
Term
|
Definition
A condition that is more common in relatives
of an affected individual than in the general population |
|
|
Term
|
Definition
Dermatoglyphic fingerprints: Derived
from the ridged skin patterns of the fingers. DNA fingerprints:
Obtained from multiple microsatellite DNA
polymorphisms |
|
|
Term
|
Definition
The 5¢ position of one pentose ring in
DNA is connected to the 3¢ position of the next pentose
via a phosphate group. The phosphodiester-sugar backbone
of DNA consists of 5¢–3¢ linkages, and this is the
direction that the nucleotide bases are transcribed |
|
|
Term
|
Definition
DNA markers on either side
of a locus; DNA sequences on either side of a gene. |
|
|
Term
| Fluorescence in situ hybridisation (FISH) |
|
Definition
Nonisotopic
method to label DNA probes for in situ hybridisation. The
ability to utilise multiple fluorochromes in the same reaction
increases the utility of this procedure. The resolving
power of FISH is further enhanced if interphase chromosomes
are studied. |
|
|
Term
|
Definition
Technique that identifies sites where there
is protein bound to DNA. This complex then becomes
resistant to degradation by nucleases. |
|
|
Term
|
Definition
Mutagenesis of the genome produces
different phenotypes. From them, it becomes possible to
detect the underlying genes; i.e., no prior knowledge of
genes is needed, and so the model is phenotype driven
(see the discussion of ENU mouse in Chapter 5 and contrast
forward genetics with reverse genetics as exemplified
by the transgenic mouse). |
|
|
Term
|
Definition
A mutation in DNA such as a
deletion or insertion which interferes with the normal
codon (triplet base) reading frame. All codons 3' to the mutation will have no meaning. For example, the triplets
GGT-TCT-GTT code for amino acids glycine, serine and
valine, respectively. A deletion of one nucleotide (e.g., a
G of the GGT) would disrupt the reading frame to give
GTT-CTG-TT, etc. The protein product will terminate
when a new stop codon is reached. |
|
|
Term
|
Definition
Cloning strategy in which knowledge
of a gene’s product (function) is used to clone the
gene. Now rarely used and replaced by positional
cloning |
|
|
Term
|
Definition
| a field of molecular biology that attempts to make use of the vast wealth of data produced by genomic projects (such as genome sequencing projects) to describe gene (and protein) functions and interactions. Unlike genomics, functional genomics focuses on the dynamic aspects such as gene transcription, translation, and protein–protein interactions, as opposed to the static aspects of the genomic information such as DNA sequence or structures |
|
|
Term
|
Definition
(Abbreviation for guanine-binding proteins.)
These proteins play an important role in relaying messages
from the cell surface to the nucleus. They act by
binding GTP (guanosine triphosphate), which leads to
activation of a second messenger system such as adenyl
cyclase. There are many G proteins including the product
of the ras proto-oncogenes. G proteins are self-regulating
since the GTP-G protein complex is hydrolysed to
inactive GDP-G protein by GTPase activity of the G
protein. More than 100 receptors convey messages
through G proteins |
|
|
Term
|
Definition
G (for Giemsa) banding used to identify
chromosomal bands in a karyotype. Spreads of cells in
metaphase are treated with trypsin and then stained with
Giemsa |
|
|
Term
|
Definition
Neomycin analogue that kills cells unless they
are neomycin resistant or carry the gene for neomycin
resistance |
|
|
Term
|
Definition
Group-specific antigen that encodes core
protein for a retrovirus |
|
|
Term
|
Definition
Prodrug that can be phosphorylated to
its active metabolite by thymidine kinase from the
herpes simplex 1 virus (HSV-tk). The active metabolite
causes cell death by inhibiting DNA synthesis |
|
|
Term
|
Definition
A sequence of DNA nucleotide bases coding for
a polypeptide. |
|
|
Term
|
Definition
The transfer of genetic material
(DNA/RNA) into the cells of an organism to treat disease
or for research purposes. |
|
|
Term
|
Definition
Colloquial term for recombinant
DNA technology: The experimental or industrial applications
of technologies that can alter the genome of a
living cell |
|
|
Term
|
Definition
An indirect measure of distance, constructed
by determining how frequently two markers
(DNA polymorphisms, physical traits or syndromes) are
inherited together. Distances in genetic maps are measured
in terms of centimorgans (see also physical map). |
|
|
Term
| Genocopy (or genetic mimic) |
|
Definition
This term is more difficult
to define and overlaps with phenocopy. It can refer
to a disorder with a similar phenotype due to abnormalities
at different genetic loci or genetic mechanisms. For
example, hereditary elliptocytosis (a disorder of the red
blood cell leading to haemolytic anaemia of variable
severity) is caused by mutations in different genes at four
loci, but each gene encodes a protein involving the red
blood cell membrane skeleton |
|
|
Term
|
Definition
The complete (haploid) genetic material
(DNA) of an organism. Hence, genomics—the study of
the structure of the genome including its DNA sequence.
Functional genomics is an additional variation in which
function is included (in contrast is genetics, which is the
study of single genes and their functions). |
|
|
Term
|
Definition
The genetic constitution of an
organism. In terms of DNA markers, it refers to the
genetic constitution of alleles at a specific locus, e.g., the
two haplotypes |
|
|
Term
|
Definition
Cells that differentiate early in embryogenesis
to form ova and sperm. |
|
|
Term
|
Definition
Term used (incorrectly) to describe the
blood spot taken from newborns by heal prick. The blood
spot is needed for newborn screening of genetic and
metabolic disorders. The name is derived from the
newborn screen for phenylketonuria, which utilises a test
called the Guthrie bacterial inhibition assay. |
|
|
Term
|
Definition
Family of genes involved in transcriptional
regulation of embryonic development. HOX genes
contain homeoboxes and determine the shape of the
body along the antero-posterior axis of the embryo.
Mutations in HOX genes cause a part of the body to be
replaced by a structure normally found elsewhere. Conserved
DNA sequences within these genes are called
homeoboxes. All vertebrates including humans have
HOX gene complexes located on different chromosomes.
Another gene family involved in development is the PAX
genes, the conserved sequence for which is called the
paired box |
|
|
Term
|
Definition
| Related to the blood; blood forming |
|
|
Term
|
Definition
Inherited disorders involving
globin, the protein component of haemoglobin. Divided
into the thalassaemia syndromes (e.g., a or b thalassaemia)
and the variant haemoglobins (e.g., sickle cell
anaemia [HbS]). |
|
|
Term
|
Definition
The chromosome number found in gametes. In
humans, this will be 23, i.e., one member of each chromosome
pair |
|
|
Term
|
Definition
A set of closely linked DNA markers at one
locus inherited as a unit |
|
|
Term
|
Definition
Having only one copy of a given genetic
locus; e.g., a male is hemizygous for DNA markers on
the X chromosome |
|
|
Term
|
Definition
Condensed, dark-appearing bands
following G (Giemsa) banding of chromosomes. Contains
predominantly repetitive DNA |
|
|
Term
|
Definition
Hybrid DNA involving two strands that
are different; e.g., there may be a base-mismatch |
|
|
Term
|
Definition
Belonging to another species, e.g., the
use of salmon sperm DNA to block non-specific hybridisation
by human DNA. |
|
|
Term
|
Definition
The presence of more than one type of
mitochondrial DNA in a cell. There are thousands of molecules
of mitochondria DNA per cell. If there is mutant
mitochondrial DNA, it can be present in varying
amounts. Some cells might have predominantly wildtype
DNA; others, predominantly mutant DNA (called
homoplasmy); and others are said to be heteroplasmic
because there is a mixture of both. Thus, phenotypic variation
between cells is possible. |
|
|
Term
| Heterozygote (heterozygous) |
|
Definition
An individual with two
different alleles (e.g., gene, polymorphic marker) at a
single locus |
|
|
Term
|
Definition
A sequence of about 180 bp near the
3' end of some homeotic genes. The 60 amino acid
peptide encoded by the homeobox is a DNA-binding
protein |
|
|
Term
|
Definition
Hybrid DNA involving two strands that
are identical |
|
|
Term
|
Definition
A form of gene targeting
on the basis of recombination between DNA sequences
in the chromosome and newly introduced identical DNA
sequences |
|
|
Term
|
Definition
Fundamental similarity, matched; e.g.,
homologous (the same) chromosomes pair at meiosis;
homology between DNA sequences means close
similarity. |
|
|
Term
|
Definition
An individual with
two identical alleles (e.g., gene, polymorphism) at
a single locus |
|
|
Term
|
Definition
Regions in genes or DNA where mutations
occur with unusually high frequency. |
|
|
Term
|
Definition
Genes that are expressed in virtually
all cells since they are fundamental to the cell’s
functions. |
|
|
Term
|
Definition
Multicentred, multinational,
multibillion dollar project. It officially started in 1990,
and its completion was announced in 2000. The project’s
major aims were to provide a complete sequence of the
human genome and the genomes of a number of model
organisms. |
|
|
Term
|
Definition
To clone DNA means to take a gene or part of a
gene and isolate it from the remainder of genomic DNA
and then produce genetically identical material. The
cloned DNA can be produced in unlimited amounts (see
also functional cloning and positional cloning; Figures
A.4, A.5, A.6). The term cloning has wider ramifications
since it also applies to the genetic duplication of cells or
even whole organisms, including potentially a human.
One method that has been used to clone various animal
species is called somatic cell nuclear transfer. |
|
|
Term
| Human leukocyte antigen (HLA) |
|
Definition
HLA is encoded for
by a multigene complex occupying approximately 3500
kb of DNA on the short arm of chromosome 6. Antigens
belonging to the HLA system are found on the surface of
all cells except the red blood cells. HLA is concerned
with normal immunological responses and plays a vital
role in graft rejection or acceptance following transplantation.
Also known as major histocompatibility complex
or MHC |
|
|
Term
|
Definition
The pairing, through complementary
nucleotide bases (A with T and G with C), of RNA/DNA
strands to produce an RNA/RNA or RNA/DNA or
DNA/DNA hybrid |
|
|
Term
| Illegitimate transcription |
|
Definition
Low transcription of a tissuespecific
transcribing gene in non-specific cells, e.g., the
detection of mRNA for the b myosin heavy chain gene (a
muscle-specific gene) in peripheral blood lymphocytes.
Also called ectopic or leaky RNA. |
|
|
Term
| Immunophenotyping (Cell marker analysis) |
|
Definition
Typing of cells with immunological markers such as
monoclonal antibodies. |
|
|
Term
|
Definition
Reversible modification of DNA that leads
to differential expression of maternally and paternally
inherited DNA or homologous chromosomes |
|
|
Term
|
Definition
The modern version of positional
cloning. Here, the discovery of a new gene is made by
using knowledge of the human DNA sequence in the
various databases and computer software. |
|
|
Term
|
Definition
Hybridisation of a DNA probe
(labelled with 3H, fluorescein or a chemical such as
biotin) to a metaphase chromosome spread or a tissue
section on a slide. |
|
|
Term
| Informative (polymorphism) |
|
Definition
Means a polymorphism is
heterozygous and so able to distinguish two alleles. In a
parental mating, at least one parent must be heterozygous
for a polymorphism to be potentially informative. If
both parents are heterozygous, the polymorphism is fully
informative—if there is a key individual to help assign
which marker co-segregates with disease, etc. |
|
|
Term
|
Definition
Proteins secreted by mononuclear leukocytes
that induce the growth and differentiation of other
haematopoietic cells. |
|
|
Term
|
Definition
Loss of DNA or part of a chromosome
that does not occupy a terminal position. |
|
|
Term
|
Definition
Segment of DNA that is transcribed but does not
contain coding information for a polypeptide (also called
intervening sequence or IVS). It is spliced out of the transcript
before mature mRNA is formed. |
|
|
Term
|
Definition
Functionally related proteins that differ
slightly in their amino acid sequence. |
|
|
Term
|
Definition
| Different forms of an enzyme. |
|
|
Term
|
Definition
An individual’s or a cell’s chromosomal constitution
(number, size and morphology). Determined by
examination of chromosomes with light microscopy and
the use of stains |
|
|
Term
|
Definition
One thousand base pairs in a sequence
of DNA. |
|
|
Term
|
Definition
One thousand daltons. A unit that
measures the molecular weight of proteins. One dalton
approximates to the molecular weight of a hydrogen
atom. The molecular weight of a protein will be based
on the sum of the atomic weights of the elements that
comprise it. |
|
|
Term
|
Definition
Statistical test to determine whether a set of
linkage data are linked or unlinked. LOD is an abbreviation
of the log10 of the odds favouring linkage. For
genetic disorders that are not X-linked, A LOD score of
+3 (1000 : 1 odds of linkage) indicates linkage, whereas
a score of -2 is odds of 100 : 1 against linkage. |
|
|
Term
|
Definition
A large number of recombinant DNA clones
that have been inserted into a vector for the purpose of
cloning a segment of DNA |
|
|
Term
|
Definition
A molecule that binds to a complementary site
on a cell or other molecule. |
|
|
Term
|
Definition
The tendency to inherit together two or
more non-allelic genes or DNA markers than are to be
expected by independent assortment. Genes/DNA
markers are linked because they are sufficiently close to
each other on the same chromosome |
|
|
Term
|
Definition
Preferential association of
linked genes/DNA markers in a population, i.e., the
tendency for some alleles at a locus to be found
with certain alleles at another locus on the same
chromosome with frequencies greater than would be
expected by chance alone |
|
|
Term
|
Definition
An in vivo or in vitro way to transfer DNA
into a cell’s nucleus. The gene of interest is mixed with
a cationic lipid suspension and then mixed with the cell
of interest. |
|
|
Term
|
Definition
Synthetic spherical vesicles with a lipid
bilayer. Function as artificial membrane systems to
deliver DNA, etc., into cells. |
|
|
Term
| Lymphoproliferative disorders |
|
Definition
Lymphomas and leukaemias
of lymphocyte origin. |
|
|
Term
|
Definition
| See human leukocyte antigen |
|
|
Term
|
Definition
One million base pairs in a sequence
of DNA. |
|
|
Term
|
Definition
| Transfers the genetic information from DNA to the ribosomes. Contains the template for polypeptide production. |
|
|
Term
|
Definition
| The global metabolic profile in any cell, tissue or organism. Some prefer the term metabonomics. |
|
|
Term
|
Definition
| A seconday tumour arising from cells carried from the primary tumour to a distant locus. |
|
|
Term
|
Definition
| Vertebrate DNA contains a small proportion of 5-methylcytosine, which arises from mehtylation of cytosine bases where they occur in the seqence CpG. The methylation status of DNA correlates with its functional activity: Inactive genes are more heavily methylated and vice versa (see also CpG islands) |
|
|
Term
|
Definition
| See RNA interference (RNAi) |
|
|
Term
|
Definition
| (See also DNA chip). Ordered, high density arrangements of nucleic acid spots. Each spot represents a different DNA probe attached to an immobile surface. Probes can be cDNA or oligonucleotides. This technology allows the simultaneuous measurement of transcriptional activity for hundred to tens of thousands of genes (i.e. transcriptome) in any cell under any condition. |
|
|
Term
|
Definition
| DNA or chromosomal deletion that is not detectable by conventional techniques such as microscopy (cytogenetics) or Southern blotting (DNA mapping) |
|
|
Term
|
Definition
| As for minisatellites, except that the polymorphism allele size is smaller (e.g. > 1kb) and the basic core repeat unit involves two to four nucleotide baes pair repeat motif. Also known as simple sequence repeats (SSRs) or short tandem repeats (STRs). One example is repeats of the motif AC-ACACACAC etc. |
|
|
Term
|
Definition
| Repeat DNA segments that comprise short head-to-tail tandem repeats giving the variable number of tandem repeat (VNTR) type polymorphisms with approximate size between 1-30 kb. VNTRs can be of two types: single locus or multilocus. The latter were used previously to construct a DNA fingerprint of an individual. |
|
|
Term
|
Definition
| A single DNA base change that leads to a codon specifying a different amino acid, e.g. the base change of GGT (glycine) to GTT (valine). |
|
|
Term
|
Definition
| Somatic cell divisions; process in which chromosomes duplicate and segregate during cell division (see also meiosis). |
|
|
Term
|
Definition
| Derived from a single clone i.e., monoclonal antibody, monoclonar lymphocyte population (see also polyclonal). |
|
|
Term
|
Definition
| Genetically identical twins formed by the division into two at an early stage in development of an embryo derived from a single fertilized egg (see dizygotic twins). |
|
|
Term
|
Definition
| A condition in which an individual or tissue has two or more cell lines of different genetic or chromosomal constitution. In contrast to a chimaera, both cell lines in a mosaic are derived from the same zygote (contrast with chimaera). |
|
|
Term
| Multidrug resistance (MDR) |
|
Definition
| Development of simultaneous resistance to multiple structurally unrelated chemotherapeutic agents (see also P-glycoprotein). |
|
|
Term
|
Definition
| Diseases that result from an interaction of environmental factors with multiple genes at diffferent loci (see also polygenic inheritance, which is sometimes used in the same sense as multifactorial). |
|
|
Term
|
Definition
| Of the mouse (latin, mus). |
|
|
Term
|
Definition
| An alteration in genetic material. this could be a single base change (point mutation)to more extensive losses of DNA (deletions) (see also missense mutation, nonsense mutation) |
|
|
Term
|
Definition
| The study of the fundamental principles of molecules and structures with at least one dimension of approximately between 1 and 100 nanometres - 1 nanometre (nm) is 1x10^-9 of a metre. |
|
|
Term
|
Definition
| A single DNA base change resulting in a premature stop codon (TAA, TGA, TAG) e.g. TCG (serine) to TAG (stop). |
|
|
Term
|
Definition
| Procedure to transfer RNA from an agarose gel to a nylon membrane (see also Southern blotting, western blotting). |
|
|
Term
|
Definition
|
|
Term
|
Definition
| Enzymes that break down nucleic acid. There are DNAase (DNAse) and RNAase (RNAse) enzymes. RNA, in particular, is susceptible to RNAases so that preparation of RNA requires a lot more care compared to the more robust DNA. |
|
|
Term
|
Definition
| The monomeric component of DNA or RNA comprising a base (adenine, thymine, uracil, guanine or cytosine), a pentose sugar (deoxyribose or ribose) and a phosphate group. |
|
|
Term
| Nucliec acid amplification technique (NAT) |
|
Definition
| Term used predominantly in microbiology to refer to the amplifiation of nucleic acids with various techniques, including PCR, ligase chain reaction, nucleeic acid sequence-baed amplification and other methods. |
|
|
Term
|
Definition
| Small single-stranded segments of DNA typically 20-30 nucleotide bases in size that are synthesised in vitro. Uses include DNA sequencing, DNA amplification and DNa probes (see also primer, allele, specific oligonucletides). |
|
|
Term
|
Definition
| Genes associated with neoplastic proliferation following a mutation or perturbation in their expression (see proto-oncogenesis, rast) |
|
|
Term
| Online Mendelian Inheritance in Man (OMIM) |
|
Definition
| An encyclopedia of phenotypes for genetic traits, disorders and gene loci estblished by Victor McKusick. Originally available on hard copy, but now the Internet version is a must because of the frequent changes that occur. |
|
|
Term
|
Definition
| Genes or proteins found in different species that are so similar in their nucleotide or amino acid sequence that they are likely to have originated from a single ancestral gene. Such genes play a core function. For example, the beta globin genes in many species are nearly identical (see also paralogous) |
|
|
Term
|
Definition
| A glycoprotein associated with multidrug resistance. A member of the ATP binding cassette transporter proteins. P-glycoprotein allows the active extrusion of a variety of compounds out of the cells. The gene for P-glycoprotein is MDR1. |
|
|
Term
|
Definition
| A tumour supressor gene, mutations of which are frequently found in human cancers. The correct name for this gene is TP53 although P53 is popularly used. |
|
|
Term
|
Definition
| Abbreviaton for paired box. Genes that play a role in the development of many tissues. These genes encode transcription factors involved in early embryological development. The paired box is a conserved DNA binding domain that resembles the paired genes of Drosophila. |
|
|
Term
|
Definition
| A DNA sequence that is identidcal in either direction. |
|
|
Term
|
Definition
| Genes in the same species that are so similar in their nucleotide sequences that they are assumed to have originated from a single ancestral gene; for example the beta and ? globin genes are paralogs. These genes have overlapping functions and arose during evolution through duplication. |
|
|
Term
|
Definition
| The development of an egg that has been activated in the absence of sperm. |
|
|
Term
|
Definition
| The steps involved in the development of a disease. |
|
|
Term
|
Definition
| All or nothing phenomenon relating to the expression of a gene. Calculated by the proportion of affected individuals among the carriers of a particular genotype. For example, if 20 out of a 100 individuals who have a known DNA mutation show the corresponding clinical phenotype, then the penetrance for this disorder is 20% (at a certain age group). |
|
|
Term
|
Definition
| The differential effects of a drug in vivo in patients, depending on the presence of inherited gene variants. |
|
|
Term
|
Definition
| The differential effects of compounds in vivo or in vitro on gene expression, among the entirety of expressed genes. However, a consistent definition of pharmacogenetics and pharmagenomics is difficult to obtain. With time, these two terms are likely to become synonymous. |
|
|
Term
|
Definition
| The combination in which polymorphic markers have been inherited within the context of a family study. |
|
|
Term
|
Definition
| An environmentally produced phenotype that mimics one caused by a genetic mutation; for example, small red blood cells (microcytosis) are similar findings in thalassaemia (genetic) and iron deficiency (environmental). Another example quited is Huntington's disease-like 1 (HDL1) which is said to be a phenocopy of Huntington's disease but is caused by familial prion disease and not an expansion of a CAG triplet repeat. The second example might also be called a genocopy. |
|
|
Term
|
Definition
Overall phenotypic characteristics of an organism based on the interaction of the complete genome with the environment (see Figure 1.4). For consistency
with the other . . . omics (genomics, proteomics,
transcriptomics, metabolomics, epigenomics), the study
of the phenome would be phenomics. |
|
|
Term
|
Definition
A map that can be constructed in different
ways, but in contrast to genetic maps, it represents
measurements of physical length (bp, kb, Mb). Types of
physical maps include cytogenetic, pulsed field gel electrophoresis,
fluorescence in situ hybridisation, contigs—
e.g., cosmid or YAC (see also genetic map). |
|
|
Term
|
Definition
Cytoplasmic, autonomously replicating extrachromosomal
circular DNA molecule. Used as vectors
for cloning. In vivo, plasmids are found in bacteria where
they can code for antibiotic resistance factors (see also
episomal, vector). |
|
|
Term
|
Definition
Used in the context of stem cell plasticity. The
potential for tissue-specific adult stem cells to differentiate
into cells of a different tissue. For example, bone
marrow differentiates into haematopoietic cells, but there is some evidence that it can also differentiate into brain,
liver and various other tissues. Transdifferentiation is
another term to describe how stem cells from one tissue
can change to adopt the developmental fate of another
tissue. |
|
|
Term
|
Definition
Different effects of a gene on apparently
unrelated characteristics such as the phenotype, organ
systems or functions. |
|
|
Term
|
Definition
The number of chromosomes in a cell. Euploid,
the correct number; aneuploid, an abnormally high or
low number; polyploid, a multiple of the euploid
number. |
|
|
Term
|
Definition
Gene that encodes reverse transcriptase
enzyme of a retrovirus (see Figure 8.2). |
|
|
Term
|
Definition
Derived from more than one cell (see also
monoclonal). |
|
|
Term
|
Definition
Trait that results from an interaction
of multiple genes at different loci (see also multifactorial
disorders). |
|
|
Term
|
Definition
polymerases are enzymes catalysing
the formation of RNA using DNA as a template. DNA
polymerases are enzymes that can synthesise DNA from
four nucleotide precursors (dATP, dTTP, dCTP and dGTP)
provided a template or primer is available to start off the
process. Functions of the DNA polymerases include
DNA repair and DNA replication. Reverse transcriptase
is also a DNA polymerase (see Figure 2.2). |
|
|
Term
| Polymerase chain reaction (PCR) |
|
Definition
DNA method allowing
amplification of a targeted DNA sequence (see Figure
2.5). |
|
|
Term
|
Definition
A segment of DNA that can
occur in two or more forms. This variation may be
detected through size differences, or the alleles can be
distinguished by changes in the nucleotide sequence.
Polymorphic variations result from point mutations (see
RFLP) or insertions of repetitive DNA sequences (see
VNTR). In terms of human genetics, polymorphisms are
inherited along mendelian lines in a family and by definition
should occur at a 1% or more frequency within a
population (see restriction fragment length polymorphism
[RFLP], variable number of tandem repeats [VNTR],
simple sequence repeat [SSR], single nucleotide polymorphism
[SNP], Table 9.2). |
|
|
Term
|
Definition
Cloning of a gene on the basis of its
chromosomal position rather than its functional properties.
Previously called reverse genetics (see clone, functional
cloning; Box 3.3). |
|
|
Term
|
Definition
Enables a mutation in DNA to be
detected in a clinically normal individual, and from this
“predict” the development of a genetic disease at some
future time. Another name for this type of test is presymptomatic
DNA test. Some prefer to use both terms, e.g.,
predictive DNA test is reserved for identifying mutations
that increase a person’s risk but provide no certainty of
developing a disorder with a genetic basis. An example
of this would be a breast cancer DNA test. In contrast,
presymptomatic DNA test can determine whether a
person will develop a genetic disorder before any signs
or symptoms appear. Examples given for the latter test
include Huntington’s disease and haemochromatosis.
However, the distinction seems unnecessarily complex
since the Huntington’s disease DNA test could be either
depending on the number of repeats (see Table 3.4). If
anything, a haemochromatosis DNA test is more predictive
than presymptomatic because of the many other
factors that influence development of this disease. Therefore,
for simplicity, the term predictive is used to describe
both types of tests. |
|
|
Term
| Preimplantation genetic diagnosis (PGD) |
|
Definition
A form of
prenatal diagnosis that involves sampling cells from
the developing embryo. Once a genetic diagnosis is
made, the embryos shown to be unaffected are transferred
to the patient by IVF. One form of PGD involves
the sampling of 1–2 cells from the 8–12 cell stage
blastomere. |
|
|
Term
|
Definition
|
|
Term
|
Definition
A short oligonucleotide segment that pairs with
a complementary single-stranded DNA sequence. The
double-stranded segment formed has a free 3¢ terminus,
which provides the template for extension into a second
strand (see oligonucleotides; Figures 2.8, A.7; contrast it
with probe). |
|
|
Term
|
Definition
Transmissible proteins that have two shapes—
the normal form (benign, showing few b sheets) and
the pathologic form that has a significant component
of b sheets. The pathologic form can spread from
one organism to another and interfere with the shape of
the normal protein, leading to neurodegenerative
diseases such as Creutzfeldt-Jakob disease (CJD) in
humans and bovine spongiform encephalopathy (BSE) in
cattle. |
|
|
Term
| Proband (or propositus or index case) |
|
Definition
The affected individual
from whom a pedigree is constructed (see also
consultand; Figure 3.13). |
|
|
Term
|
Definition
A single-stranded segment of DNA or RNA
labelled with a radioactive or chemical substance. The
probe will bind to its complementary single-stranded
target sequence. Hybrids formed are detectable by
autoradiography or by chemical changes. There are a
number of different probes: genomic, cDNA, RNA,
oligonucleotide. The naming of probes has led to confusion.
Therefore, an attempt to induce uniformity has been
made by naming loci to which probes will hybridise; e.g.,
D15S10 indicates human chromosome 15 locus 10. A
number of DNA probes could hybridise to this locus (see
Figure A.10). |
|
|
Term
|
Definition
Bacteria and certain algae with cells that
are not nucleated. |
|
|
Term
|
Definition
DNA sequence located immediately 5¢ to a
gene, which indicates the site for transcription initiation.
May influence the amount of mRNA produced and the
tissue specificity. Examples of promoters are the TATA,
CCAAT boxes (see also Cap). |
|
|
Term
|
Definition
All the proteins in a cell, tissue or organism
at any given time. Hence, the field of proteomics, which
unlike the constancy found in DNA (all nucleated cells
have the same DNA content), is made considerably more
complex because the proteome is different for each cell,
and even the same cell can change its protein profile
depending on environmental effects, e.g., infected and
non-infected cell |
|
|
Term
|
Definition
Normal genes comprising a number
of functionally different classes that are involved in cellular
growth control. Altered forms of the protooncogenes
are called oncogenes |
|
|
Term
|
Definition
Virus that is integrated into the chromosome
of its host cell and can be transmitted from one generation
to another without causing lysis of the host (see retrovirus,
reverse transcriptase). |
|
|
Term
| Pulsed field gel electrophoresis (PFGE) |
|
Definition
A type of gel
electrophoresis allowing large fragments of DNA to be
separated by altering the angle at which the electric
current is applied. Now used mostly for microbiologic
DNA fingerprinting. |
|
|
Term
|
Definition
The use of PCR to quantitate
DNA (see real-time PCR, Figure 2.7). |
|
|
Term
| Quantitative trait loci (QTL) |
|
Definition
Genes that control the
expression of traits demonstrate quantitative inheritance and are mapped to QTLs. Complex characteristics—for
example, height in humans and hypertension—are QTLs
that result from the interaction of a number of genes on
separate chromosomes (the environment also plays a
role). |
|
|
Term
|
Definition
(Also called RNA mediated
gene silencing and post-transcriptional gene silencing.)
The process by which small RNA species can regulate
gene function. These species include small doublestranded
RNA (dsRNA) species known as small interfering
RNAs (siRNA) that target mRNA and micro RNAs
(miRNA) that work at the level of translation (see Figure
2.3) |
|
|
Term
|
Definition
A family of proto-oncogenes (H-ras-1, K-ras-2 and
N-ras) that encode for a protein called p21. p21 binds to
GTP/GDP and has GTPase activity. Ras-derived proteins
play a physiological role in regulation of cellular proliferation.
Mutations in ras are found in a number of
cancers (see also G proteins). |
|
|
Term
|
Definition
A variant of PCR that monitors the
amplified product as it is produced after each cycle in
real time. Has proven to be an invaluable technique for
quantitative PCR (see Figure 2.7). |
|
|
Term
|
Definition
The products of both normal (wild-type)
alleles at a particular locus are non-functional in a recessive
disorder (see also dominant; Figure 3.9). |
|
|
Term
|
Definition
| (rDNA) technology (Ch. 1) |
|
|
Term
|
Definition
Crossing over (breakage and rejoining)
between two loci, which results in new combinations of
genetic markers/traits at those loci; e.g., one locus has
four genetic markers linearly arranged as a-b-c-d, and the
second locus is b-b-c-a. Recombination involving these
two regions between the b-c markers would give new
genetic combinations, i.e., a-b-c-a and b-b-c-d (see
Figure 2.15). |
|
|
Term
|
Definition
A group of genes that monitor and repair
DNA errors. There are three major repair pathways: (1)
mismatch repair, (2) nucleotide excision repair and (3)
base excision repair (see Table 3.6). |
|
|
Term
|
Definition
(Also called Cloning-to-Produce-
Children.) The use of technology such as somatic cell
nuclear transfer to produce an animal (child) with a virtually
identical genetic makeup to another animal
(human) existing or previously existing (see also clone,
therapeutic cloning; Figure 6.9, Table 6.14). |
|
|
Term
| Restriction endonucleases (enzymes) |
|
Definition
Enzymes that
recognise specific short DNA sequences and cleave DNA
at these sites (see Table A.1). |
|
|
Term
| Restriction fragment length polymorphism (RFLP) |
|
Definition
Biallelic
DNA polymorphism that results from the presence
or absence of a restriction endonuclease site (see polymorphisms;
Table 2.6, Figure 2.13). |
|
|
Term
|
Definition
A series of restriction endonuclease
recognition sites associated with a DNA locus or gene
(see Figure A.2). |
|
|
Term
|
Definition
RNA virus that utilises reverse transcriptase
during its life cycle. After infecting the host cell, the retroviral
(RNA) genome is transcribed into DNA, which is
then integrated into host DNA. In this way the retrovirus
can replicate (see also provirus, reverse transcriptase;
Figure 4.8). |
|
|
Term
|
Definition
A term once used to describe positional
cloning (see also clone, functional cloning, in silico
cloning; Figure A.4). Reverse genetics is now used to
describe animal models that are genotype based, i.e., the
transgenic mouse in which a gene is manipulated to
provide information on the resulting phenotype (see
Chapter 5) |
|
|
Term
|
Definition
Enzyme that enables synthesis of
single-stranded DNA (called cDNA) from an RNA template
(see also polymerase; Figure 2.2). |
|
|
Term
|
Definition
The RNA content of ribosomes.
The latter are small cellular particles that are the
site of protein synthesis in the cytoplasm. |
|
|
Term
|
Definition
The use of rRNA-specific DNA probes for
hybridising to restriction fragments to distinguish bacteria
on the basis of their rRNA patterns. Polymorphic
bands so produced allow typing of bacteria at the strain
level. |
|
|
Term
|
Definition
Sry-type HMG box. Developmental and differentiation
genes with transcription factor activity and
characterised by having a HMG (high mobility group)
DNA binding domain. |
|
|
Term
|
Definition
Sex determining region Y. The gene on the Y chromosome
that specifies maleness in humans. |
|
|
Term
|
Definition
Short head-to-tail tandem repeats that
incorporate specific DNA motifs (see microsatellites,
minisatellites; Table 2.6, Figure 2.13, Table 9.2). |
|
|
Term
|
Definition
Testing individuals on a population
basis to identify those who would be at risk for
disease or transmission of a genetic disorder (see Tables
2.8, 2.9). |
|
|
Term
|
Definition
The proportion of those with disease who
test positive (see also specificity; Tables 2.10, 8.3). |
|
|
Term
| Sequence tagged site (STS) |
|
Definition
A way to provide unambiguous
identification of DNA markers generated by the
Human Genome Project. STSs comprise short, singlecopy
DNA sequences that characterise mapping landmarks
on the genome. |
|
|
Term
|
Definition
Establishing the identity and order
of nucleotides in a segment of DNA. The gold standard
in characterising a mutation (see Figures A.7, A.8). |
|
|
Term
|
Definition
A group comprising the brothers and sisters
(siblings) in a family. |
|
|
Term
|
Definition
Transfer of signals from extracellular
factors and their surface receptors by cytoplasmic
messengers to modulate events in the nucleus (see also
G proteins). |
|
|
Term
|
Definition
| (SSR) See microsatellites. |
|
|
Term
Single nucleotide polymorphism (SNP—pronounced
snip) |
|
Definition
Variations of a single nucleotide at a given
position in the genome in a population that, by definition,
occurs at a frequency greater than 1% (see also
polymorphism). SNPs occur approximately 1 in each
600–1000bp, so in the human genome the number of
SNPs will be significantly greater than 3.3 ¥ 106 (see
Figure 2.13). |
|
|
Term
| Somatic cell genetic disorders |
|
Definition
One of the five groups
of genetic disorders. Defects in DNA are found in specific
somatic cells. An example of this type of disorder is
sporadic cancer. By comparison, the four other categories
(single gene, polygenetic, multifactorial and chromosomal
disorders) have the genetic abnormality present
in all cells including the germ cells. |
|
|
Term
|
Definition
A hybrid formed from the fusion
together of different cells. They usually come from different
species; e.g., human and rodent hybrids are frequently
used for human gene mapping. |
|
|
Term
| Somatic cell nuclear transfer (SCNT) |
|
Definition
The introduction
of nuclear material from a somatic cell (the donor DNA)
into an oocyte (recipient) that has had its nucleus
removed. This yields a product (clone) that has the
genetic (nuclear) constitution which is virtually identical
to the donor of the somatic cell (see also clone, human
cloning; Figure 6.9). |
|
|
Term
|
Definition
Any cells in an organism which are not
germ cells, i.e., sperm or eggs. |
|
|
Term
|
Definition
A mutation occurring in any cell that
will not become a germ cell. |
|
|
Term
|
Definition
Named after E Southern. Describes
the procedure for transferring denatured (i.e., singlestranded)
DNA from an agarose gel to a solid support
membrane such as nylon (see northern blotting, western
blotting). |
|
|
Term
|
Definition
The proportion of those without disease
who test negative (see also sensitivity; Tables 2.10, 8.3). |
|
|
Term
|
Definition
| Removing introns to produce mature mRNA. |
|
|
Term
|
Definition
| No obvious genetic cause. |
|
|
Term
|
Definition
Nucleotide codon (ATG) that is positioned
at the beginning of a gene sequence in eukaryotes.
Prokaryotes do not have such a start codon, and so ATG
is translated into the amino acid methionine. |
|
|
Term
|
Definition
Cell with the capacity for (1) self-renewal,
i.e., giving rise to more stem cells, and (2) generating
different progeny (see embryonic stem cells, adult stem
cells). |
|
|
Term
|
Definition
Fragments of double-stranded DNA with a
few bases not paired; i.e., they anneal with greater
efficiency than blunt-end fragments (see Table A.1). |
|
|
Term
|
Definition
Nucleotide codons (TAA, TGA and TAG)
positioned at the 3¢ end of a gene sequence that indicate
the termination of a polypeptide. |
|
|
Term
|
Definition
Because the genetic code is degenerate (a
change in the third nucleotide may still produce the same
amino acid, Tables 2.1, 2.5), single base changes may not
alter the amino acid sequence, and they are called synonymous (i.e., same sense) codons. In contrast are
non-synonymous changes, which produce a different
amino acid. |
|
|
Term
|
Definition
Genetic loci or genes that lie on the
same chromosome or same DNA strand. |
|
|
Term
|
Definition
repeats Small sections of repetitive DNA in the
genome, arranged in head-to-tail formation. |
|
|
Term
|
Definition
The two ends of a chromosome (see centromere;
Figure 2.10) |
|
|
Term
|
Definition
(Also called Cloning-for-Biomedical-
Research.) Production of a human embryo by a process such
as somatic cell nuclear transfer for the purpose of research
or for the extraction of stem cells. The ultimate goal in this
type of cloning is to gain scientific knowledge for medical
research (see also clone, reproductive cloning; Figure 6.9,
Table 6.14). |
|
|
Term
|
Definition
In contrast to the cis-acting locus,
the trans-acting locus involves a second but distinct gene
that can influence another gene’s function through production
of a regulatory-type protein. |
|
|
Term
|
Definition
Synthesis of a single-stranded RNA molecule
from a double-stranded DNA template in the
nucleus (see polymerase, translation). |
|
|
Term
|
Definition
All mRNA species in a cell, tissue
or organism at a given time. Like the proteome, this is
very variable compared to the fixed genome (see also
microarray). |
|
|
Term
|
Definition
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Term
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Definition
Transmission of genetic material
from one cell to another by viral infection. |
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Term
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Definition
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Term
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Definition
Acquisition of new genetic markers by
incorporation of added DNA into eukaryotic cells by
physical or viral-dependent means (see Figure
6.1). |
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Term
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Definition
Provides the link between mRNA
and rRNA. Each tRNA can combine with a specific
amino acid and also bind to the relevant mRNA codon
(see also codon, messenger RNA [mRNA], ribosomal
RNA [rRNA], translation). |
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Term
| Transformation (of bacteria) |
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Definition
Acquisition of new
genetic markers by incorporation of added DNA into
bacteria. |
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Term
| Transformation (of cells) |
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Definition
Sudden change in a cell’s
normal growth properties into those found in a tumour
cell. |
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Term
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Definition
The presence of foreign DNA in the
germline. Transgenic animals are produced by experimental
insertion of cloned genetic material into the
animal’s genome. This can be done by microinjection of
DNA into the pronucleus of a fertilised egg or through
utilisation of embryonic stem cells. A proportion of transgenic
animals will express the foreign gene and transmit
it to their progeny (see embryonic stem cells). |
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Term
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Definition
Change of a purine (i.e., adenine or guanine)
to a purine or a pyrimidine (i.e., cytosine or thymine) to
a pyrimidine (see also transversion). |
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Term
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Definition
Cytoplasmic production of a polypeptide
from the triplet codon information on mRNA (see
transcription). |
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Term
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Definition
The presence of a segment of a chromosome
on another chromosome (see Figure 4.10). |
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Term
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Definition
DNA sequences that can move
from one chromosomal site to another. |
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Term
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Definition
A type of transposable element that is
flanked by repeat sequences. Transposons usually possess
genes, for example, with resistance to antibiotics. Transposons
allow for genetic recombination, thereby enhancing
genetic diversity. An interesting observation from the
Human Genome Project was the finding that hundreds
of human genes appear to have derived from transposable
elements. |
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Term
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Definition
Change of a purine to a pyrimidine or vice
versa (see also transition). |
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Term
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Definition
(Also called recessive oncogenes,
anti-oncogenes, growth suppressor genes.)
Normal genes with one component of their function
being the suppression of tumourigenesis (see P53; Figures
4.11, 4.12). |
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Term
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Definition
The inheritance of two copies of a
chromosome from the one parent. This can be isodisomy synonymous (i.e., same sense) codons. In contrast are
non-synonymous changes, which produce a different
amino acid. Described with
a number of human chromosomes, e.g., 7, 11, 15, 16
(see also imprinting; Figure 4.6). |
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Term
| Variable number of tandem repeats (VNTR) |
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Definition
A multiallelic
DNA polymorphism that results from insertions or
deletions of DNA between two restriction sites (see polymorphisms;
Table 2.6, Figure 2.13, Table 9.2). |
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Term
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Definition
Cloning vehicle (i.e., plasmid, phage, cosmid or
YAC) into which DNA to be cloned can be inserted (see
Figure A.5). |
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Term
| Western blotting (immunoblotting) |
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Definition
A technique used
to separate and identify proteins (see northern blotting,
Southern blotting). |
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Term
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Definition
The form of the gene normally present
in nature. |
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Term
| X-chromosome inactivation |
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Definition
Random inactivation of
one of the two female X chromosomes during early
embryonic development. Thus, cells in a female are
mosaic in respect to which of the X chromosomes is
functional. |
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Term
| Yeast artificial chromosome (YAC) |
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Definition
A cloning vector
that allows large segments of DNA (e.g., 300 kb in size)
to be cloned. |
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Term
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Definition
A new model organism allowing the study of
genetic disease particularly in relation to development.
One unusual property of this model is that organs are
visible during development. |
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Term
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Definition
Infections transmitted from animals to
humans. |
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Term
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Definition
The diploid cell resulting from union of the
haploid male and haploid female gametes, i.e., fertilised
ovum. |
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Term
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Definition
Hepatitis B virus e antigen (HBeAg)—a part
of the core antigen of the hepatitis B virus (HBcAg) that
is secreted into the serum through cellular secretion pathways.
HBeAg correlates strongly with infectivity. |
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Term
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Definition
(small interfering RNA) see RNA interference
(RNAi). |
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Term
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Definition
| Process in which diploid germ cells undergo division to form the haploid chromosome number (see also mitosis) |
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