In humans, dominant alleles control whether you can roll your tongue (R) and whether you have a widow’s peak (W).  People homozygous for the recessive alleles (r and w) cannot roll their tongues and do not have a widow’s peak.  Suppose a tongue-rolling woman with a widow’s peak marries a man who cannot roll his tongue and does not have a widow’s peak.  The first child of this couple cannot roll his tongue and does not have a widow’s peak.  What are the genotypes of the father, mother, and child?

Father’s genotype         ____________________           Mother’s genotype       ___________________

Child’s genotype           ____________________                                                       

When determining the probability of the inheritance of two independent traits (on different chromosomes), it is oftentimes easier to use the multiplication rule than a Punnett Square. The  states that the probability of two (or more) independent events occurring together is the product of their individual probabilities.  

Use the multiplication rule to determine the probability of this same couple having a second child that can roll her tongue and has a widow’s peak.