I PCR out a mutated gene in a patient with Lisenbee chorea (the inability to dance in a coordinated fashion) and I compare it to another patient with that same disease phenotype. One subject had a mutation on chromosome 4, and the other subject couldn't rock it because of a mutation on chromosome 5. This is an exampe of




A.pleitropy



B.locus heterogeneity



C.allelic heterogeneity



D.dominant negative mutation



E.penetrance

E. penetrance

The correct answer is B. locus heterogeneity.

Locus heterogeneity refers to the phenomenon where different genetic mutations at different loci can cause the same disease phenotype. In this case, both patients have the same disease phenotype of Lisenbee chorea (inability to dance in a coordinated fashion), but they have mutations in different chromosomes (one on chromosome 4 and the other on chromosome 5). This demonstrates locus heterogeneity, as different loci are contributing to the same phenotype.

To determine the correct answer, let's break down the information given in the question:

- One patient with Lisenbee chorea has a mutation on chromosome 4.
- Another patient with Lisenbee chorea has a mutation on chromosome 5.

Based on this information, we can analyze the options provided:

A. Pleiotropy: Pleiotropy refers to a single gene having multiple effects on different traits or systems in an organism. This does not seem to apply to the scenario described in the question.

B. Locus heterogeneity: Locus heterogeneity occurs when mutations at different genetic loci can cause the same phenotype or disease. This is a possibility since the mutations in the two patients are at different locations (chromosomes 4 and 5).

C. Allelic heterogeneity: Allelic heterogeneity refers to different mutations at the same genetic locus leading to the same phenotype or disease. This does not apply to the scenario since the mutations are on different chromosomes.

D. Dominant negative mutation: A dominant negative mutation is a type of mutation where the mutant gene product interferes with the function of the wild-type gene product, often resulting in a dominant pattern of inheritance. The information provided does not indicate the dominance or recessiveness of the mutations.

E. Penetrance: Penetrance refers to the proportion of individuals with a specific genotype who show the expected phenotype. Although the question mentions mutations in patients with a particular disease phenotype, it does not provide information about the penetrance of these mutations.

Based on the information provided, the most appropriate answer is B. Locus heterogeneity, as the mutations in the two patients are at different genetic loci (chromosomes 4 and 5).