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| An enzyme that wraps complete around a DNA duplex and creates a single-stranded break by breaking the phosphodiester bond. This can either increase or decrease the amount of super coiling. |
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| An enzyme creates a double stranded gap that allows one duplex molecule to pass through the other, relaxing the super coiling. |
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| The paradox that genome size does not correlate with organism complexity. |
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| A way DNA makes up for the tension formed by supercoliling the DNA, so it twists the actually molecule in the opposite way the DNA is twisted to release tension. |
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| Consists of octamer of histone proteins: 2 x of each: H2A, H2B, H3, H4 |
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| The role Histone protin H1 plays. |
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Definition
| H1 is not in the actual nuclesome core particle, it is instead used outside of it. In addition it is only a monomer, not used in 2x. In addition, H1 is used as to combine linker DNA between adjacent core particles. This histone out of the 5 that has a noticably different amino acid sequnence. |
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| Found in nuclei of cells of the salivary glands of drosophlilla, way larger than the other somatic cells chromosomes found during metaphase. |
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| Tandem repeat DNA found in chromosomes. Mostly found in heterochromatin. |
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| Non coding sequenecs usually found here. Its main role is to protect the chromosome and regulate the gene. Very tightly packed. |
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| Rich in gene concentration, mostly the region that codes for proteins and good stuff like that. This region is not as tighly packed as heterochromatin. |
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Definition
Each arm of the chromosome occupies a discrete space. It's important to note this space is disrupted when cells are divided, by are remade in the following interphase. Note however chromosome territories may be different in different types of cell.
Choromsome territories are correlated with gene density. The territories of chromatin that have a relatively low gene density are located near the edge of the nucleus. While the territories with high gene density are located near the center of the nucleus |
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| The end of the chromosomal arms. Posses a problem in DNA replication due to lagging strand being continually deleted, eventually it would delete useful genes. This is however solved through the enzyme telomerase. |
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Definition
Discovered by Carol Grieder & Elizabeth Blackburn. What it does it adds DNA tandem repeats to the 3' end of DNA strands in telomere regions. Telomerase is a reveres transcriptase that carries its own RNA molecule, which is used as a template when it elongates telomeres, which are then shorted after each replication cycle.
Telomerase has both DNA and RNA componets, so what it does it uses its RNA componet to bind to DNA site. Then the DNA polymerase function of telomerase then creates a few repeats. Telomerase then translocates to the newly formed strand and cycle is continued until it reaches a sufficient length. Then DNA primase goes in the opposite direction sets up an RNA Primier then DNA polymerase fills in the gaps. |
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Definition
| The metaphase spread of chromosomes. Goes from longest to shortest, with the single sex chromosomes at the end. make 22 pairs of autosomal chromosomes, and 1 pair of sex chromosomes. Making a total of 46 chromosome. |
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| G-bands used to describe areas of chromsomes: |
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Definition
Short arm of chromosome: p for petite
Long arm of chromosome:q for `not petite`
1p34
1= Regions on the chromsome
34= actual gene on the chomrsome. |
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| General Forms of Chromosomes Typical: |
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Definition
Metacentric: centromere in the middle,arms equal length. During anaphase makes a "v" shape
Submetacentric: centromere slightly off from center. During anaphase makes a "j" shape.
Acrocentric: centromere near the one of ends of the chromosome. During anaphase makes an "i" shape. |
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| General Forms of Chromosomes Atypical: |
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Definition
Acentric: no centromere. Unstable because cannot be moved properly during cell division.
Dicentric: Two centromeres. The chromosome is usually stretched and broken during causing them to be unstable. However, there is an exception when the centromers are physically close to another another, then they transmit as a unit. |
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Term
| Dosage Compensation of X-linked Gene |
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Definition
Because males have only one X chromosome, and females have 2 X, the dosage of the genes expressed on those genes need to be controlled. Either increased for the male, or decreased in the female.
X- inactivation (female): In the embryo @ approx 64-128 cell stage, only 1 X chromosome (chosen at random) in each cell to remain active, the rest stay inactive. This causes all subsequent daughter cells to do the same.
This process begins at the site XIC (X-inactivation center) causing a bend. This site includes a transcribed region called X-inactivation-specific transripit (Xist). Causing: Heavy cytosine methylation in 5’ regulatory regions of genes, aggregation of heterochromatin-specific DNA-binding proteins, Deacetylation and methylation of histones.
This random choosing of the inactivation of one of the x-chromosomes results in a female mosaic x chromosome, ex calcio cats. |
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Term
| Pseudoautosomal inheritance |
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Definition
*Generally found at tips of long and short arms
*Pseudoautosomal regions = regions of shared homology between the X and Y
*Crossing over takes place 20x greater than the autosomes
* Thus, pseudoautosomal inheritance refers to a gene that shows autosome-like patterns of inheritance but are known to reside in pseudoautosomal region |
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Definition
| set of alleles at 2 or more loci present in a particular chromosome. This is particularly useful for reconstructing lineages on the y-chromsome, as there is no recombination, so genetic markers are passed from generation to generation. |
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Definition
| set of alleles at 2 or more loci present in a particular chromosome. This is particularly useful for reconstructing lineages on the y-chromsome, as there is no recombination, so genetic markers are passed from generation to generation. |
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Definition
| Refers to an otherwise diploid organism that has an extra copy of an individual chromosome. |
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| Chromosome abnormalities in pregnancy, aneuloid vs euploid. |
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Definition
15 % of all pregnacies result in spontaneous abortion. Half of these cases are caused by chromosome abnormalities, many of which are trisomic. As stated most trisomic mutations result in abortion, the exception are trisomy 13,18 and 21. 13, and 18 result in severe developmental abnormalities and infant survive weeks at most. Trisomy 21 causes the condition known as down syndrome.
This extra chromosome causes gene dosage to be out of equilibrium due to the extra chromosome, this is called aneuoloid. Differs from euploid which has the same gene dosage as found in a diploid organism, for example a tripoiad of teraploid 3 and 4 copies of each chromosome. |
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Definition
| 1 in 750 live births. Trisomy-21 results in 3/4 abortion, the 1/4 = the ratio 1/750 live births. Trisomy-21 usually is caused by non-disjuction of chromosome-21 during meiosis. Causing one gamete to have both chromosomes, and the other to have 0. |
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Term
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Definition
| A chromosomal aberration resulting from the interchange of parts between nonhomologous chromosomes |
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Definition
| euploid condition wherein non-homologous chromosomes have an interchange of part, but all parts are present |
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Definition
aneuploid condition in which some part of genome is missing
Balanced translocation is less detrimental than unbalanced |
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Term
Chromosome deletion/deficiency
ectopic recombination |
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Definition
Usually harmful, the larger the deletion the more damage it does. Can be caused by double-stranded breaks to the DNA backbone.
Can also be caused by homologous recombination between repeated DNA sequences present at different sites along the DNA, a process known as ectopic recombination. Ectopic= abnormal positioning. |
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Definition
| Caused by ectopic positioning during prophase 1, causing unequal crossing over to occur. Tandem duplication is a region of the chromosome repeated twice. |
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Term
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Definition
chromosome in which linear order of a group of genes is the reverse of normal order.
Formed by either:
1.Two-break event in which middle segment is reversed in orientation
2.Ectopic recombination between sequences that are inverted repeats |
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Term
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Definition
Inversion includes the centromere
Both products of crossover are monocentric
One chromatid carries duplication of a and deletion of d, the other duplication of d and deletion of a
Duplication and deletion usually cause inviability, products of recombination usually not recovered |
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Term
| Translocation, heterozygous vs homozygous |
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Definition
If a translocation, which is a interchange of genetic material from non homologous chromosomes, is heterzygous (one normal pair of chromsomes, one traslocated) then the offspring will display semisterility (half as many off spring produced). Homozygous translocation results in complete sterility.
Both these cause the gametes to be anuelopid. |
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Term
| Robertsonian translocation |
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Definition
A nonreciprocal translocation. Two nonhomologous acrocentric chromosomes undergo fusion of their short arms, end result is chromosome with a single functional centromere
Especially relevant to human genetics
If chromosome 21 is one of the acrocentrics in a Robertsonian translocation, can lead to familial type of Down’s, risk of recurrence very high |
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Definition
| A field of study dealing with the DNA sequence, organization, function, and evolution of genomes |
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Definition
| All of the genetic information, the entire genetic complement, all of the hereditary material possessed by an organism (Even better) |
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Definition
| Allopolyploids are polyploids with chromosomes derived from different species. |
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Definition
| Autopolyploids are polyploids with multiple chromosome sets derived from a single species. |
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| Type of cuts made by restriction enzyme. |
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Definition
A a-symmetrical cut results in a "stick end".
A symmetrically cut results in a a blunt end. |
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Term
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Definition
| an unusual polymerase that can bind to a single-stranded RNA and use as a template for the synthesis of a complementary strand of DNA. Call cDNA. |
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