Methods of inheritance

Multiple alleles Blood type gene – 3 alleles, 4 phenotypes Alleles are IA, IB, I Phenotypes are type A, B, AB & O IA & IB are co dominant over O

Autosomal Recessive Diseases Requires two bad alleles to show trait Albinism Cystic fibrosis Phenylketonuria (PKU) Sickle cell Tay Sachs

Autosomal Dominant Disease Huntington’s chorea Symptoms usually don’t appear until around age 40 HH or Hh have trait hh don’t have the trait

Sex – linked diseases Hemophilia Color blindness Both are recessive so females need two bad alleles to show trait but males only need one.

Incomplete dominance Snapdragon flowers get there color from co dominant alleles which also show incomplete dominance. CR is the color allele for red CW is the color allele for white Heterozygous = Pink