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

Question

Quizplus · Accepted Answer

The exceptional individual has nail-patella syndrome but is homozygous for the A allele of the marker, which is only found in individuals without the syndrome. This suggests that recombination has occurred between the nail-patella gene and the marker gene in one of the exceptional individual's parents, resulting in the exceptional individual inheriting two copies of the A marker allele but only one copy of the nail-patella disease-causing allele.

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