The A and B genes are on nonhomologous chromosomes. A zygote is formed by the fusion of a sperm with the genotype AB and an egg with the genotype ab. The zygote develops into a male. Which of the following are genotypes of sperm that could be produced by this male?

AB and ab only

AB, ab, Ab and aB only

AB only

ab aB and Ab only

AB, ab, Ab and aB

Explanation:

The zygote has the genotype AaBb because it was formed by the fusion of a sperm cell AB and an egg ab.

During meiosis the diploid AaBb germ cell will reduce its chromosome number by half, producing a total of 4 haploid daughter cells (the gametes, in males the sperm cells) with just one allele per gene. The genes A and B are on different chromosomes, so they assort independently, and 4 types of gametes can therefore be produced: AB, Ab, aB and ab.