Term
| Maternal effect (snail coiling) |
|
Definition
An inheritance pattern for certain nuclear genes (located on chromosomes found in cell nucleus) in which the genotype of the mother directly determines the phenotypic traits of her offspring(F1). F2 mothers' genotypic ratio of 1DD:2Dd:1dd. F3 generation 3:1.
You need to know the genotype of the mother to predict phenotypic outcome. |
|
|
Term
|
Definition
| Nurse cells which are diploid produce gene products that are transported into the oocyte and influence the early developmental stages of the embryo. The gene products,mRNA,and proteins don't last a very long time before they are degraded so they can only exert their effects during early stages of embryonic development. |
|
|
Term
|
Definition
| Pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression but not permanently |
|
|
Term
|
Definition
| The phenomenon that the level of expression of many genes on the sex chromosomes(particularly X)are similar in both genders even though males and females have different numbers of sex chromosomes |
|
|
Term
| Mechanisms of dosage compensation |
|
Definition
| Random inactivation of 1 X chromosome in female mammals; it becomes inactivated at early stage of embryonic development and condensed to form a Barr body; the embryonic inactiviation is remembered so that the same X chromosome is inactivated in all daughter cells; can produce a variegated phenotype for heterozygous females |
|
|
Term
| Lyon's hypothesis that adult female heterozygous for fast and slow G-6-PD alleles should express only one of the two alleles. |
|
Definition
| Data show all nine clones expressing either fast or slow alleles. Each clone was a population of cells independently derived from a single epithelial cell and since they were obtained from an adult female, the hypothesis predicts that each epithelial cell would already have one of its X chromosomes permanently inactivated and would pass this trait to its progeny cells. |
|
|
Term
| X-inactivation in mammals depends on the Xic locus and Xist gene. |
|
Definition
| Xic region contains a gene that encodes an RNA Xist. This RNA is transcribed from the inactivated X chromosome and coats it leading to its compaction. During early embryonic development, the nonactivated X chromosome expresses the TsiXgene, which encodes an antisense RNA that inhibits the effects of the Xist Rna. |
|
|
Term
| Three phases of X inactivation. Counting human X chromosomes is accomplished by counting the number of Xics. |
|
Definition
1. initiation-targeted inactivation
2. spreading-condensation
3. maintenance |
|
|
Term
|
Definition
| A type of marking process in which a gene or chromosome is only expressed depending on the gender of the parent from which it was inherited. Mouse Igf-2 gene, imprinting occurs so that paternal allele is expressed. You need to know whether the mutant Igf-2 allele is inherited from the mother or father to predict dwarfism in offspring. |
|
|
Term
| Three stages of imprinting. Imprinting is permanent in somatic cells but from generation to generation |
|
Definition
| 1. establishment of the imprint during gametogenesis 2. maintenance of the imprint during embryogenesis and in adult somatic cells 3. erasure and reestablishment of imprint in the germ cells |
|
|
Term
| DNA methylation is mechanism for gene imprinting |
|
Definition
| When male makes gametes, the imprinting is erased during early spermatogenesis so that a male can pass either active allele to offspring. The erasure also occurs during early oogenesis in females, but de novo methylation occurs in both genes so that females transmit inactive alleles to offspring. |
|
|
Term
| Imprinting plays a role in Prader-Willi syndrome and Angelman syndrome |
|
Definition
| A region on chromosome 15 contains 2 closely linked but distinct genes that are maternally or paternally imprinted. If the maternally expressed gene is deleted, will lead to AS. If paternally expressed gene is deleted, will lead to PWS. If the gene is silenced they get the disease. |
|
|
Term
| Extranuclear or cytoplasmic inheritance |
|
Definition
| in mammals located in mitochondria and in plants located in plastids |
|
|
Term
|
Definition
| the location of genetic material of mitochondria and chloroplasts/human mitochondrion that is a circular DNA molecule 17,000 bp in length containing genes that encode rRNA,tRNA,and 13 genes encoding polypeptides/chroloplast genome is circular molecule containing 156,000 bp and 110-120 different genes including those encoding rRNA,tRNA and proteins required for photosynthesis |
|
|
Term
| Reciprocal cross for extranuclear traits (examines relationship btwn transmission of a trait and gender of the parents) |
|
Definition
| Organelles do not segregate in the same way during oogenesis compared with spermatogenesis. The mitochondria and plastids are not transmitted via the gametes in the same way for both sexes. In ex. of 4-o'clock plant, offspring resemble female parent. Variegated phenotype due to mixture of plastids in female parent. |
|
|
Term
| Petite mutants as evidence for extranuclear inheritance |
|
Definition
| Segregational petite mutants involve mutations ingenes located in nucleus. Vegetative petite mutants do not segregate in Mendelian manner because involve mutations in mitochondrial genome. 2 types of vegetative petites are neutral and suppressive. Neutrals lack most of mitochondrial DNA and suppressives lack small segments of mitochondrial genetic material. |
|
|
Term
| Pattern of inheritance of mitochondria and plastids varies among species |
|
Definition
The inheritance of organelles may be maternal, paternal or biparental.
Mitochondrial mutations can cause human diseases. Leber's hereditary optic neuropathy is a human mitochondrial disease: To predict this you need to know whether the mother has this trait because the offspring will inherit her mitochondria(maternal inheritance). |
|
|
Term
| Origin of mitochondria and chloroplasts |
|
Definition
| Endosymbiosis theory: mitochondria from purple bacteria and chloroplasts from cyanobacteria |
|
|
Term
| To determine the normal chromosomal composition of a species |
|
Definition
| Cytogeneticist microscopically examines the chromosome to obtain a karyotype or photograph in which all chromosomes w/in a single cell have been lined up in a standard way. Each species has its own characteristic number of chromosomes |
|
|
Term
| 3 features used to identify chromosomes |
|
Definition
1. size
2. location of centromere
3. banding patterns |
|
|
Term
| Ways to alter chromosome structure plus experimental ways |
|
Definition
| 1. changing amount of material(Deficiency or Duplication) or rearranging the material(Inversion or Translocation). Reciprocal translocation involves interchange of material btwn 2 different chromosomes and simple translocation occurs when a single piece of chromosome is attached to another chromosome. Also use of colchine,cell fusion and production of monoploids. |
|
|
Term
| Loss of genetic material in deficiency is detrimental |
|
Definition
| Phenotypic consequences depend on size of deletion and what genes it includes. Causes too few copies of several genes. Deficiencies can be detected using cytological, genetic and molecular techniques.Pseudodominance can sometimes reveal deletions b/c 1 copy of a gene has been deleted from a chromosome and the remaining copy of a recessive allele on the homologous chromosome is phenotypically expressed. The individual is hemizygous for the recessive allele. |
|
|
Term
| Phenotypic consequences of duplications |
|
Definition
| Correlated with size and are less harmful than deletions. They also can add more genes to a species genome and promote the formation of gene families such as globin gene family. Evolution of traits allows genes to be more specialized in their function. |
|
|
Term
| Position effect in bar-eye phenotype in Drosophila |
|
Definition
| Effect on the expression of a gene when its location in a chromosome is changed, often by translocation. |
|
|
Term
| Pericentric inversion/Paracentric inversion |
|
Definition
| when centromere lies within inverted region of chromosome/centromere outside of inverted region. No phenotypic consequences. |
|
|
Term
| Inversion heterozygotes contain 1 normal and 1 inverted chromosome |
|
Definition
| may yield unusual cross over products during meiosis depending on location of crossover and percentric vs. paracentric. |
|
|
Term
| Unbalanced translocations/Balanced or reciprocal |
|
Definition
| Detrimental phenotypic effects, causes too many copies of several genes./no phenotypic consequences because the individual has a normal amount of genetic material. Two nonhomologous chromosomes break creating reactive ends that bind to each other. Also, two nonhomologous chromosomes can crossover with each other(At meiosis in a reciprocal translocation heterozygote, the passage ( segregation) of both normal chromosomes to one pole and both translocated chromosomes to the other pole, giving genetically balanced gametes). |
|
|
Term
| Translocation cross and 3 types of segregation |
|
Definition
| The pairing of homologous regions leads to structure with four pairs of sister chromatids due to reciprocal translocations. 1.Alternate=Segregation of centromeres during meiosis in a reciprocal translocation heterozygote such that genetically balanced gametes are produced. 2.Adjacent-1=segregation of non-homologous centromeres during meiosis in a reciprocal translocation heterozygote such that unbalanced gametes with duplications and deficiencies are produced) 3.Adjacent-2=segregation of homologous centromeres during meiosis in a translocation heterozygote such that unbalanced gametes with duplications and deficiencies are produced)(very rare) |
|
|
Term
| Aneuploidy causes an imbalance in gene expression that is often detrimental to the individual's phenotype |
|
Definition
| A cell or organism does not have an exact multiple of a chromosomal set and is an abnormal condition. |
|
|
Term
|
Definition
| Aneuplodies in humans usually involve small or sex chromosomes. Trisomies(2n+1) and monosomies(Cri du chat) of autosomes produce lethal phenotypes that cause early spontaneous abortion. Aneuploidy is influenced by age of parent(Down syndrome-inheritance of 3 copies of chromosome 21-) |
|
|
Term
| Natural variations in eulploidy |
|
Definition
| Male bees contain a single set of chromosomes but female bees are diploid |
|
|
Term
|
Definition
| certain somatic cells become polyploid in a diploid organism. ex. are polytene chromosomes found in Drosophila. Increases number of chromosomes 1000-fold. Large size and banding pattern. |
|
|
Term
|
Definition
| having 3 or more sets of chromosomes is common in plants because they are more robust than diploids and may be seedless.Occurs due to abnormal cell division during metaphase I in meiosis. |
|
|
Term
| Meiotic nondisjunction can produce aneuploid gametes. Complete meiotic nondisjunction could produce a diploid gamete and thereby produce a polyploid offspring. |
|
Definition
| Mitotic nondisjunction or chromosome loss can produce anueploid or polyploid somatic cells. AN organism with a mixture of genetically different cells is a genetic mosaic. |
|
|
Term
| Changes in euploidy(exact multiple) can occur by 1.autopolyploidy 2.alloploidy 3.allopolyploidy |
|
Definition
| 1. Nondisjunction can produce an individual with 1 or more extra sets of chromosomes from the same/single species. 2.interspecies mating btwn related species(common)produces A hybrid individual or cell having two or more sets of chromosomes derived from two different species. 3.an allopolyploid contains 2 or more sets of chromosomes from 2 or more species(polyploid produced by the hybridization of two species) and is a combination of autopolyploidy and alloploidy. |
|
|
Term
| Allodiploids(two genetically distinct sets of chromosomes derived from different ancestral species) and allotetraploids(a hybrid that has a chromosome set 4 times that of a haploid organism. Allotetraploids are created as a result of both chromosome sets of each parents being present in gametes) |
|
Definition
| often sterile (exception when from closely related species, called homeologous) b/c do not have chromosomes that are found in homologous pairs making it difficult to separate during meiosis./More likely to be fertile. |
|
|
Term
| Experimental treatments can promote polyploidy |
|
Definition
| Abrupt temperature changes during initial stages of seedling growth;treatment of plants with colchine can cause complete nondisjunction and thereby produce polyploidy |
|
|
Term
|
Definition
| 1.Treat diploid plant with colchine and allow to grow 2.Take a cutting of the tetraploid portion 3.root the cutting in soil and tetraploid plant will grow |
|
|
Term
| Cell-fusion techniques used to make hybrids(allopolyploid) |
|
Definition
| 1.Treat plant cells from 2 species with agents to digest cell wall creating protoplasts 2.Cause cells to fuse creating a heterokaryon that will go thru a nuclear fission process to create a HYBRID cell with a single nucleus 3.Culture hybrid cells to create individual allopolyploid plants. |
|
|
Term
| Use of monoploids in agricultural and genetic research to create homozygous and hybrid strains |
|
Definition
| Anther culture technique:produces monoploid plants which are converted to diploids by colchine treatment. These diploids are homozygous for all their genes b/c they were produced from monoploids |
|
|
Term
| Intersitial vs. Terminal deficiency |
|
Definition
|
|
Term
|
Definition
| Two parallel crosses that involve the same genotypes of the 2 parents, but their sexes are opposite in the 2 crosses. For ex. female BB x male bb and a reciprocal cross in which female bb x male BB. Autosomal inheritance gives the same result b/c the autosomes are transmitted from parent to offspring in the same way for both sexes. For maternal inheritance the reciprocal crosses would show that the gene is always inherited from the mother. |
|
|
Term
| X-inactivation and phenotype of calico cat |
|
Definition
| The pattern of black and orange fur is due to random X inactivation during embryonic development. The orange patches are due to inactivation of the X chromosome that carries a black allele and the black patches are due to inactivation of the X chromosome that carries the orange allele. |
|
|
