Incomplete Penetrance. Some genes are incompletely penetrant.
Sex-limited genes are ones that are inherited by both men and women but are normally only expressed in the phenotype of one of them. The heavy male beard is an example.
Pleiotropy. A single gene may be responsible for a variety of traits.
Multiple alleles. Mendel studied just two alleles of his pea genes, but real populations often have multiple alleles of a given gene. Incomplete dominance. ... Codominance. ... Pleiotropy. ... Lethal alleles. ...
