Genetics with Dr. Sotoro chapter 04-Extensions pt1

Alleles

Different variants of a gene that map to the same locus on homologous chromosomes.

Null allele

A mutant allele that causes the absence of gene product or gene product function due to a loss-of-function mutation.

Wild type

The most common phenotype of a species as it occurs in nature.

Incomplete dominance

A type of inheritance where heterozygous individuals have a phenotype that is an intermediate of the two contrasting traits.

Penetrance

The frequency with which individuals of a given genotype manifest at least some degree of the trait.

Expressivity

The degree or range in which a phenotype for a given trait is expressed.

Pleiotropy

A condition in which a single mutation causes multiple phenotypic effects.

Marfan syndrome

autosomal dominant mutation in fibrillin, a gene that codes for a connective tissue protein present in many tissues in the body.

Essential gene

A gene that is necessary for growth and survival; its absence results in lethality.

Lethal allele

An allele that results in the death of an organism when present in a homozygous state.

Multiple alleles

The existence of more than two allele variants for a given gene.

Codominance

A mode of inheritance in which both alleles contribute to the phenotype of an organism.

A and B antigens are carbohydrate groups that are bound to..

lipids on the surface of erythrocytes

Epistasis

A phenomenon where the effect of one gene masks or modifies the effect of another gene.

Recessive epistasis

A form of epistasis where the recessive allele of one gene masks the effects of alleles of another gene.

Dominant epistasis

A form of epistasis where the dominant allele of one gene masks the phenotypic expression of another gene.

Complementation

The occurrence when two parents exhibiting a recessive phenotype can yield offspring with a dominant phenotype due to different recessive alleles.