Why can human genetics be represented the way we set up Mendels laws for peas?
• We do not have populations of humans that are purebred like commercial peas. • A pea plant may produce hundreds of peas. Today humans usually produce two children. • You can mate any pea plant to any other pea plant. Humans either select their own mates or very strict cultural rules determine who marries whom. • How then do we represent human traits for breeding analysis? • We use a pedigree which we construct from a family history. • In a family history we ask questions about a trait that may or may not run in a family and try to include as many relatives as is feasible (usually three generations). • In a pedigree we use symbols to diagram the relation among the family members. These include a square for males; a circle for females; and a filled in square or circle for an affected individual (one who shows some unusual trait). • Do Mendel’s rules apply to pedigrees? • Yes, and we can represent the genotypes and phenotypes the same way. The major difference is in the P1 which does no