The squares in the table represent the genotypes of the children that could be produced by all possible combinations of these eggs and sperm. Can you determine the phenotypes of each individual child based on these genotypes? Be careful and consider which traits are expressed as dominant or recessive conditions. Hemophilia is X-linked recessive, nail patella is autosomal dominant, and xeroderma pigmentosum is autosomal recessive.

In the production of eggs and sperm we did not consider the possibility of crossing over. Since the gene loci of nail patella and xeroderma pigmentosum are both located on chromosome #9, we say they are linked. In this case we made the assumption that they would be inherited together on the same #9 chromosomes. We did not take into consideration the possibility of crossing over between the two #9 chromosomes during meiosis.

Since the male model is homozygous for both loci this would not affect the genetic makeup of his sperm. However, the female is heterozygous for both the nail patella and xeroderma loci so there could be other genetic combinations in her eggs if crossing over between these two loci does occur. She could occasionally produce eggs that contained N_p and X_D or N_P and X_d. This would increase the genetic variation possible in the children produced by these two people.