Chapter 3, Problem 19P

Using old Fugate family Bibles and the Perry County, Kentucky historical record, a hematologist in the 1960s constructed the pedigree of the Blue People of Troublesome Creek. Many members of the Fugate family had blue skin, a rare but harmless condition known as methemoglobemia; other people in the pedigree had blue lips and fingertips but their skin was otherwise normal. The blue color is due to lack of function of the enzyme NADH diaphorase, which repairs hemoglobin damaged by oxidation. Unrepaired hemoglobin accumulates as blue pigment.

a.	Based on the pedigree, describe the dominance relation between the wild-type and mutant alleles of the gene for NADH diaphorase.
b.	The pedigree indicates certain people who were known to have only blue lips and fingertips. However, the historical record is incomplete. Which other people in the diagram must have had this phenotype? Explain any ambiguities that exist. (In case you’ve already read Section 3.3, assume that the blue lip and fingertip phenotype is fully penetrant.)
c.	Two of the matings in the pedigree are shown as possibly consanguineous, as indicated by a dotted horizontal line above a solid horizontal line. The reason for the uncertainty is that the historical record does not say whether or not Mary [Mary (?)], the wife of the Martin Fugate at the top left of the diagram, was a Ritchie or a Smith or was instead unrelated to either family. Explain why a geneticist would think that Mary is likely a Ritchie or a Smith.
d.	All of the Blue People (people with methemoglobemia) in the pedigree are Fugates, yet the blue mutation did not originate in the Fugate family. Which person or people introduced the mutant NADH diaphorase allele(s) into the Fugate family?