Topic 11 - Extension of Mendelian Inheritance

Pleiotropy

Single gene affects multiple phenotypic traits.

Carriers

Individuals with one recessive allele, not expressing it.

Sex-linked Genes

Genes located on sex chromosomes, influencing traits.

Hemizygous

Having only one allele for a gene.

Y-linked Genes

Genes found exclusively on the Y chromosome.

Pseudo-autosomal Inheritance

Genes present on both X and Y chromosomes.

Reciprocal Cross

A cross where parental phenotypes are reversed.

X-linked Recessive Trait

A trait more likely to affect males.

Expressivity

Degree of phenotype expression among individuals.

Multinomial Expansion Equation

Formula for calculating probabilities with multiple outcomes.

Dominant epistasis

Dominant allele masks effects of another gene.

Epistasis

One gene masking the effect of another.

Complementation

Producing wild type offspring from two mutants.

Autosomal Traits

Traits determined by genes not on sex chromosomes.

Incomplete Penetrance

Dominant allele may not express phenotype in heterozygotes.

Lethal Alleles

Alleles that can cause death, often recessive.

Incomplete Dominance

Heterozygote shows intermediate phenotype between homozygotes.

Codominance

Both alleles expressed equally in heterozygotes.

Overdominance

Heterozygote exhibits greater vigor than homozygotes.

X-linked Inheritance

Traits linked to genes on the X chromosome.

Sex-influenced Inheritance

Traits influenced by the sex of the individual.

Sex-limited Inheritance

Traits expressed only in one sex.

Essential Genes

Genes necessary for survival; absence causes death.

Nonessential Genes

Genes not required for survival.

Conditional Lethal Alleles

Kill organisms only under specific environmental conditions.

Heterozygote Advantage

Heterozygotes have benefits over homozygotes.

Intermediate Phenotype

Phenotype that is a blend of two extremes.

Gene modifier effect

Alleles modify phenotypic effects of another gene.

Recessive epistasis

Recessive allele suppresses another gene's expression.

Suppressor mutation

Mutation that reverses effects of another mutation.

Intergenic suppressor

Suppressor mutation in a different gene.

Environmental influence

Impact of environment on phenotype expression.

Norm of reaction

Phenotypic range under varying environmental conditions.

Cumulative effect

Combined effect of multiple genes on phenotype.

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