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Exam 1 Genetics
| Term | Definition |
|---|---|
| chromosome | means colored body; nuclear DNA passed on through gametes by males and females |
| karyotype | an arrayed set of banded chromosomes |
| diploid | 2 copies of each type of chromosome; produced by the fusion of 2 gametes, one from the female and one from the male |
| homologous chromosome | members of a chromosome pair |
| nonhomologous chromosome | chromosomes from different pairs |
| metacentric chromosome | the arms are about equal in length |
| submetatacentric | one arm is shorter that another |
| acrocentric | one arm is extremely short |
| telocentric | centromere is at the end of a single arm |
| G1 | the cell prepares for DNA and chromosome replication |
| G2 | the cell prepares for cell division |
| S | DNA replication |
| Interphase | individual chromosomes are elongated; centrioles are replicated |
| meiosis | process of two successive divisions of a diploid nucleus with one DNA replication cycle resulting in the formation of haploid gametes |
| Prophase 1 | chromosomes become shorter and thicker, crossing over occurs, spindle apparatus forms, nuclear membrane and nucleolus disappear |
| leptonema | early prophase, chromosomes visible, sister chromatids present, cell committed to meiosis |
| zygonema | homologous chromosomes begin to pair and twist around another |
| pachynema | "thick strand", chromosomes very condensed and synapsed, crossing over takes place |
| diplonema | chromosomes begin to move apart |
| diakineses | chiasmata often terminalize; easiest time to count chromosomes |
| Metaphase 1 | nuclear membrane has broken down, spindle apparatus is formed, tetrads align on equatorial plate |
| Anaphase 1 | chromosomes in each tetrad seperate |
| Telophase 1 | tetrads complete their migration to opposite poles |
| Prophase 2 | chromosome contraction |
| Metaphase 2 | centromeres divide and sister chromatids become seperate chromosomes lined up on the equatorial plate |
| Anaphase 2 | centromeres and chromosomes are pulled to opposite spindles |
| Telophase 2 | nuclear membrane forms around the chromosomes and cytokinesis takes place |
| gene | the basic unit of inheritance |
| allele | an alternative form of a gene or region of DNA |
| locus | the location or position on a chromosome of a particular gene |
| Dominance | where the phenotype of the heterozygote is the same as the dominant homozygote |
| Recessive | for the phenotype to be expressed, both alleles must be homozygous |
| Law of Independent Assortment | genes assort independently during meiosis |
| Complete Dominance | a form of dominance in which the expression of the heterozygote is identical to the expression of the homozygous dominant genotype |
| Partial Dominance | the expression of the heterozygote is intermediate to the expressions of the homozygous genotype; favors towards the dominant |
| No dominance/codominance | the expression of the heterozygote is exactly halfway between the phenotype of the homozygotes |
| Overdominance | the expression of the heterozygote is outside the range definded by the phenotype of the homozygous dominant genotypes |
| Epistasis | occurs when the phenotypic expression of a gene at one locus is affected by the alleles of a gene at another locus |
| Sex-linked inheritance | when the gene responsible for the phenotype is located on a sex chromosome |
| sex-limited trait | phenotypic expression is limited to one sex |
| sex-influenced inheritance | phenotypic expression is influenced by the gender of the animal |
| breeding value | the collective genetic merit of an animal when all of its genes are considered |
| heritability | measures the strength of the relationship between the trait and the breeding value |
| performance testing | systematic measurement of performance in a population |
| Accuracy | measure of the strength of the relationship between the true value and the prediction |
| simply-inherited | traits that are affected by only a few genes |
| polygenic traits | controlled by many genes |
| mating | the process that determines which males will be bred to which female(s) |
| complementarity | an improvement in the overall performance in the offspring resulting from mating individuals with different but complimentary breeding values |
| crossbreeding | mating of sires of one breed to dams of another breed |
| allele frequency | the relative abundance or rarity of an allele in a population |
| random mating | a system in which each individual has an equal opportunity to mate with any individual of the opposite sex |
| migration | movement of breeding animals from one population into another pop where the allele frequencies differ |
| genetic drift | changes is gene frequency caused by CHANCE segregation of an allele into the gametes |
| quantitative traits | traits that are measured with numbers on a continuous scale |
| threshold traits | traits where the underlying genetic level has to reach a certain point before phenotypic expression changes |
| fitness | the ability to survive and reproduce |
| Phenotypic value | measure of performance for a trait in an individual |
| Genotypic value | Effect of an individual's genes on its performance for a trait |
| Environmental effect | effect that external (nongenetic) factors have on animal performance |
| Population mean | average phenotypic value of all individuals in a population |
| Independent/additive gene effects | effect of an allele is independent of the effect of the other allele at the same locus and the effects of epistatsis |
| gene combination value | the part of an individual's genotypic value that is due to the effects of combination of genes |
| temporary environmental effect | environmental effect that influences a single performance record of an individual, but does not permanently affect the individual's performance for a repeated trait |
| paramters | summary numbers that describe the whole population; constant; generally unknown |
| statistics | summary numbers calculated from samples and are estimates of parameters |
| variance | a measure of dispersion or differences |
| standard deviation | the square root of the variance; average deviation from the mean |
| covariance | population measure that measures the deviations from the means of two variables |
| correlation | a standardized measure of the the degree of the relationship between 2 traits |
| phenotypic correlation | relationship between the performance in one trait and the performance of another |
| genetic correlation | strength of the relationship between the BV fro one trait and the BV for another |
| regression coefficient | the units of change in Y per unit of change in X |
Created by:
aly486
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