| A | B |
|---|
| allele frequency | proportion of all copies of a gene in a population that are a given allele type |
| codominance | when alleles for a gene are expressed equally |
| complementary gene action | when two genes work together to produce a particular phenotype |
| complementation test | method to find out whether a phenotype is the result of mutation in one or two genes |
| conditional lethal | an allele whose expression is fatal under certain environmental conditions |
| continuous trait | when an inherited trait exhibits many intermediate forms |
| discontinuous trait | phenotypes expressed in discrete varieties |
| epistasis | expression of allele of one gene masks expression of alleles of another gene |
| expressivity | degree to which a particular phenotype is produced by a given genotype |
| heterogeneous trait | a given phenotype is caused by mutation in one of several genes |
| histocompatiblity antigens | cell surface proteins that participate in self-recognition |
| incomplete dominance | phenotype of heterozygote is intermediate to homozygous parents |
| inhibitor | allele whose presence blocks expression of another trait |
| lethal mutation | allele whose expression is fatal |
| modifier genes | a gene whose expression alters phenotype by affecting expression of other gene alleles |
| monomorphic | a gene with only one wild-type allele |
| multifactorial | phenotype determined by two or more factors |
| mutant alleles | alleles generated by changes in DNA sequence |
| penetrance | proportion of individuals with a given phenotype exhibiting the expected phenotype |
| permissive range | environmental conditions that generate a particular phenotype |
| phenocopy | change in phenotype caused by environmental conditions - mimics mutation |
| pleiotropy | single gene determines a number of unrelated traits |
| polygenic | traits controlled by multiple genes |
| polymorphic | genes with more than one wild-type allele |
| quantitative traits | another name for continuous traits |
| recessive epistasis | when a recessive allele masks the expression of another gene |
| recessive lethal | gene allele that is fatal only in the homozygous condition |
| restrictive range | environmental conditions that prevent expression of a given phenotype |
| wild-type allele | the designated "normal" gene allele |
