Nail-patella syndrome is an autosomal disorder affecting the shape of nails on f

Question

Nail-patella syndrome is an autosomal disorder affecting the shape of nails on fingers and toes, as well as the structure of kneecaps. The pedigree shows the transmission of nail-patella syndrome in a family along with ABO blood type. Is nail-patella syndrome a dominant or a recessive condition? Does this family give evidence of genetic linkage between nail-patella syndrome and ABO blood group? Why or why not? Using N and n to represent alleles at the nail-patella locus and I^A, I^B, and i to represent ABO alleles, write the genotypes of I-1and I-2 as well as their five children in generation II. Why does III-6 have nail-patella syndrome and III-8 not have the disorder? Give genotypes for these two individuals, III-6 and III-8. Give genotypes for III-11 and III-12. The genotypes cannot be unambiguously determined.

Explanation / Answer

A. The trait nail-patella is a dominant autosomal trait as the trait is seen in every generation.

B. Yes, the family does show the linkage between the syndrome and the ABO blood group.

C. this is because linkage can be seen if the loci for both the traits is very close, which seems possible. The nail-patella trait moves along with the same blood group A.

D. The genotypes are as follows:

E. Though the trait shows a linkage between the trait and the blood group A, but it is possible that the trait is passed on but the blood group is different. Since the trait is autosomal dominant the single allele is capable of showing the trait and does not require the blood group to be necessary to be A. So when the dominant allele for the trait is present it shows the trait.

F. The genotype of the III-6 and III-8 is Nn, ii and nn, ii.

G. The genotypes of III-11 and III-12 is Nn, IA i and nn, IA i

generation genotype I-1 nn, ii I-2 Nn, IAi II-2 nn, ii II-4 Nn, IAi II-6 Nn, IAi II-7 nn, ii II-9 Nn, IAi

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