Chapter 13b - Exceptions to Mendel's Principles

Autosome

Chromosomes 1-22

Sex chromosome

Chromosomes X or Y

Hemizygous

Having only one allele for a trait, such as men for X-linked traits

Carrier

A heterozygote for a recessive trait

Linked genes

Genes that are on the same chromosome

Incomplete dominance

Heterozygotes that have a phenotype intermediate between the homozygous dominant and homozygous recessive phenotypes

Codominance

Heterozygotes that express both phenotypes equally

Epigenetics

Genetic effects that are not directly due to a change in the DNA sequence

X-linked inheritance

Inheritance pattern of genes that are located on the X chromosome

Autosomal inheritance

Inheritance pattern of genes that are NOT located on the X chromosome

X-linked

Gene on the X chromosome

Lethal allele

Recessive allele that is not viable: homozygous recessive individuals die

Epistasis

Effect of the expression of one gene on the expression of another gene