Question: A plant line with reduced fertility comes to the attention of a plant breeder who observes that seed pods often contain a mixture of viable seeds that can be planted to produce new plants, and withered seeds that cannot be sprouted. The breeder examines numerous seed pods in the reduced fertility line and counts 622 viable seeds and 204 nonviable seeds.

Part A
What single-gene mechanism best explains the breeder’s observation?

A) Homozygous dominant or recessive genotype results in withered seed.
B) Heterozygous genotype results in withered seed.
C) Homozygous recessive genotype results in withered seed.
D) Incomplete dominance of alleles that results in viable seed.
E) Incomplete dominance of alleles that results in withered seed.
F) Homozygous dominant genotype results in withered seed.