1. Flower color in snap dragons is governed by two alleles that show incomplete dominance. Determine the genotypes and the phenotypes in the offspring of the following crosses:
a. Red x White
b. Pink x Pink
c. Pink x White
d. Pink x Red
Since the inheritance of flower color in snapdragons is governed by incomplete inheritance, let’s first designate the alleles and the genotypes for the different plants: Red = RR, White = WW and Pink = RW. You may also opt to use r for white, so that the white-flowered snapdragons will be rr and the pink-flowered ones Rr. In either case, it’s important to remember that the heterozygote exhibits a phenotype that is distinct from the dominant and the recessive traits.
RR x WW --> RW; all the offspring will be have pink flowers
RW x RW --> 1RR:2RW:1WW; 1 red:2 pink:1 white
RW x WW --> 1RW:1WW; 1 pink:1 white
RW x RR --> 1RR:1RW; 1 pink:1 red

2. ABO blood type is governed by a multiple allele system. Identify the blood types among the offspring if you cross a male with type AB blood with a female with type O blood.
There are three alleles for the ABO blood type: IA, IB and i. IA encodes for the production of antigen A on the surface of RBCs, IB for the production of antigen B and i, for the absence of these antigens. An individual that has type AB blood has both the alleles for the production of antigens A (IA) and B (IB), thus the father in this problem has the genotype IAIB. On the other hand, the mother, has blood type O which means that she does not have either antigens A or B, resulting from a genotype of ii.
So this cross written out will be: IAIB x ii
The father can produce two types of gametes, IA and IB; while the mother can only produce one type, i. The allele combinations that are possible in the resulting offspring are IAi and IBi, so the offspring can have either type A or type B blood.

3. A rooster with gray feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are gray, 6 are black and 8 are white. What is the simplest explanation for the inheritance of these colors in chickens? What offspring would you predict from the mating of a gray rooster and a black hen?
The pattern of inheritance described in this problem is most likely incomplete dominance. The phenotypic ratio of the offspring approximates 1:2:1 (6 black-feathered:15 gray-feathered:1 white-feathered), which is characteristic of this type of inheritance. In addition, of course, there is a third distinct phenotype (gray) that is exhibited by the heterozygotes, which is a blend of black and white phenotypes exhibited by the homozygotes.
A cross between a gray (BW) rooster and a black (BB) hen would result in half of the offspring possessing gray feathers (BW) while the other half would have black feathers (BB).

4. A man with type A blood marries a woman with type B blood. Their child has type O blood. What are the genotypes of these individuals? What other genotypes, and in what frequencies, would you expect in offspring from this marriage?
The blood types of each parent are given, so we already know that the mother, having type A blood, can have a genotype of either IAIA or IAi; while the father, having type B blood, can be either IBIB or IBi. But since their child has type O blood, then we can conclude that both mother and father each have the recessive allele i, in order to have such a child. And since we now know what their phenotypes are: IAi for the mother and IBi for the father, we can predict the offspring that may result from this cross: the genotypic ratio would then be 1 IAIB:1 IAIB:1 IBi:1 ii.