Term | Definition |
genetics | the science of heredity and of the mechanisms by which traits are passed from parents to offspring |
heredity | the passing of genetics traits from parents to offspring |
trait | a genetically determined variant of a characteristic. |
pollination | the transfer of pollen from the male reproductive structures to the tip of the female reproductive structure of a flower in angiosperms or to the ovule in gymnosperm. |
self-pollination | the transfer of pollen grains from an anther to the stigma of the same flower or to the stigma of another flower on the same plant |
cross-pollination | a reproductive process in which pollen from one plant is transferred to the stigma of another plant |
true-breeding | describes organisms or genotypes that are homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait. |
P generation | parental generation, the first two individual that mate in a genetic cross. |
F1 generation | the first generation of offspring obtained from an experimental cross of two organisms |
F2 generation | the second generation of offspring obtaining from an experimental cross of two organisms the offspring of the F1 generation. |
dominant | describes the allele that is fully expressed when carried by only one of a pair homologous chromosomes. |
recessive | describes a trait or an allele that is expressed only when two recessive alleles for the same characteristics are inherited. |
law of segregation | Mende's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosomes from each pair is preset in each gamete. |
law of independent assortment | the law that states that genes separate independently of one another in meiosis. |
molecular genetics | the study of the structure od nucleic acid and the function and regulation of genes. |
allele | one of the alternative forms of a gene that governs a characteristic, such as hair color |
genotype | the entire genetic makeup of an organism; also the combination of genes for one or more specific traits. |
phenotype | an organism's appearance or other detectable characteristic that results from the organism's genotype and the environment |
homozygous | describes an individual that has identical alleles for a trait on both homologous chromosomes. |
heterozygous | describes an individual that has two different alleles for a trait |
probability | the likelihood that a possible future event will occur in any given instance of the event; the mathematical ratio of the number of times one outcome of any event is likely to occur to the number of possible outcomes of the event |
monohybrid cross | a cross between individuals that involves the pair of contrasting traits |
Punnett square | a graphic used to predict the results of a genetic cross |
genotypic ratio | the ratio of the genotypes that appear in offspring |
phenotypic ratio | the ratio of phenotypes produced by a cross |
testcross | the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype |
complete dominance | a relationship in which one allele is completely dominant over another |
incomplete dominance | a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully. |
codominance | a condition in which both alleles for a gene are fully expressed |
dihybrid cross | a cross between individuals that have different alleles for the same gene |