Chapter 11, Problem 43P

Mutations in the HPRT1 gene in humans result in at least two clinical syndromes. Consult OMIM (www.omim.org) by querying HPRT1; you will only need to look briefly at the top three hits (files #300322, 300323, and 308000).

a.	What is the full name of the HPRT1 enzyme?
b.	On which chromosome is the HPRT1 gene located?
c.	Mutations in HPRT1 are associated with two different syndromes. What are these syndromes? For each answer the following questions: (i) what are the symptoms associated with the syndrome? (ii) is the mutant allele that causes the syndrome dominant, recessive, codominant, or incompletely dominant with respect to the normal allele, or do special conditions apply? (iii) Is the syndrome associated with a loss-of function or a gain-of-function disease allele? (iv) does the syndrome display allelic heterogeneity? (v) does the syndrome display locus heterogeneity? (Note: You do not need to understand everything in the OMIM enteries to answer these questions.)