Biology Terms Vocabulary

Allele: molecular forms of a gene that are formed by the union and code for different versions of the same trait.

Codominance: In heterozygotes, pair of nonidentical alleles that specify different phenotypes.

Continuous Variation: in a population, a range of small differences in trait among its individuals.

Dihybrid Cross: A union between two F1 heterozygotes that are identical for two gene loci; the dihybrids are offspring of parents that bred true for different versions of two traits.

F1: The offspring of an initial genetic cross.

F2: The offspring of parents who are the first generation from a genetic cross.

Gene: Information for a heritable trait, passed from generation to generation.

Genotype: Genetic constitution of an individual.

Heterozygous: is when the pair of alleles are different; --->(Aa)

Homozygous Dominant: is when the pair of alleles are identical; example --> (AA)or (BB)

Homozygous Recessive: is when the pair of allels are recessive and are identical; example --> (aa) or (bb).

Hybrid Offspring: offspring having a pair of nonidentical alleles for a trait.

Incomplete Dominance: Condition in which one allele of a pair is not fully dominant.

Independent Assortment: Mendelian theory that when meiosis ends, each pair of homologous chromosomes are sorted before shipment to gametes independently of how the other pairs were sorted. Later modified to account for the disruptive effect of crossing over on linkages.

Monohybrid Cross: Union between two F1 heterozygotes that are identical for one gene locus.

Multiple Allele System: Three or more slightly different molecular forms of a gene that occur among individuals of a population.

Phenotype: Observable trait or traits of an individual that arise from gene interactions and gene-environment interactions.

Pleiotropy: Positive or negative effects on two or more traits owing to expression of alleles at a single gene locus.

Probability: is a way of expressing knowledge or belief that an event will occur or has occurred.

Punnett-square method: Construction of a diagram as a way to predict probable outcomes of a genetic cross.

Segregation: Mendelian theory. Sexually reproducing organisms inherit pairs of genes, those two genes of each pair are separated from each other at meiosis, and they end up in separate gametes.

Testcross: Experimental cross to determine whether an individual of unknown genotype that shows dominance for a trait is either homozygous dominant or heterozygous.

True-breeding lineage: a lineage in which only one version of a trait appears over the generations in all parents and their offspring.