Biology Chapter 12 Key Terms

gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes

in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic

inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them

trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait

antagonistic interaction between genes such that one gene masks or interferes with the expression of another

underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism

having two different alleles for a given gene on the homologous chromosome

having two identical alleles for a given gene on the homologous chromosome

in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype

species or biological system used to study a specific biological phenomenon to be applied to other different species

observable traits expressed by an organism

phenotypic characteristic caused by two or more genes

visual representation of a cross between two individuals in which the gametes of each individual are denoted along the top and side of a grid, respectively, and the possible zygotic genotypes are recombined at each box in the grid

trait that appears “latent” or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed

inheritance pattern in which an allele is only lethal in the homozygous form; the heterozygote may be normal or have some altered, nonlethal phenotype

cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait