Solutions For An Introduction to Genetic Analysis Chapter 2 Problem 12P

The given Figure shows a typical pedigree of a dominant phenotype and every part of the pedigree demonstrates Mendel's first law of segregation. It includes the separation of alleles into gametes. The ratio that could not be confirmed in the pedigree is due to small size of the families. But the allele segregation is very clear.

In generation II, the middle part of pedigree shows a typical test cross.

The cross of an individual of unknown heterozygosity with a fully recessive parent is called a test cross.

In this case, the parents are homozygous (a/a) and heterozygous (A/a). If the progeny of such marriage is totaled, a 1:1 ratio is expected of the unaffected (a/a) to the affected (A/a) persons. But the equal segregation of the allele is very obvious.