Imagine That You Are Searching for the Gene Associated with Nail-Patella

Multiple Choice

Imagine that you are searching for the gene associated with nail-patella syndrome, a dominant genetic disorder that causes developmental abnormalities. In a large pedigree you discover an association between nail-patella syndrome and a genetic marker that occurs in two different alleles, A and B. Fifteen individuals within this pedigree have nail-patella syndrome and are A/B heterozygotes for the marker. Thirty individuals within this pedigree don't suffer from nail-patella syndrome and are homozygous for the A marker allele. One individual within this pedigree has nail-patella syndrome and is also homozygous for the A marker allele. The most likely explanation for this exceptional individual is that ________.

A) a new mutation converted the disease-causing allele to the wild-type form
B) a new mutation converted the B allele of the marker to the A form
C) the exceptional nail-patella individual is haploid
D) recombination occurred between the nail-patella gene and marker locus in one of the parents of the exceptional individual