Campbell Biology 11th Edition by Lisa Urry,Michael Cain,Steven Wasserman,Peter Minorsky,Jane Reece

Exercise 27

For pedigree problems, use the tips in Figure 14.15 and below to determine what kind of trait is involved.
a. If parents without the trait have offspring with the trait, the trait must be recessive and the parents both carriers.
b. If the trait is seen in every generation, it is most likely dominant (see the next possibility, though).
c. If both parents have the trait, then in order for it to be recessive, all offspring must show the trait.
d. To determine the likely genotype of a certain individual in a pedigree, first label the genotypes of all the family members you can. Even if some of the genotypes are incomplete, label what you do know. For example, if an individual has the dominant phenotype, the genotype must be AA or Aa ; you can write this as A-. Try different possibilities to see which fits the results. Use the rules of probability to calculate the probability of each possible genotype being the correct one.