PLSC 631 - Intermediate Genetics

Molecular Markers Quiz

1. Huntington's Disease is a dominant disease that affects the nervous system of an affected individual and will lead to premature death. A molecular marker (G8) was reported to be tightly linked to the disease-causing gene. When the DNA in the vicinity of G8 was analyzed with the restriciton enzyme HindIII, the following restriction map was constructed. This map shown in the figure below represents all of the HindIII sites that were located in populations of individuals from all over the world. Below the map is the RFLP pattern obtained from homozygous individuals. Number the HindIII from 1-7, left to right. For each genotype, determine which HindIII sites are responsible for its unique RFLP pattern. (5 pt)

A large family with individuals who have Huntington's disease was analyzed with the G8 probe. Each individual was scored for their RFLP genotype and for the disease. The table below gives the results. From the table determine which (if any) allele (that is A,B,C, or D) is linked to the disease. Also determine if any members of this population contain a recombinant chromosome. (5 pt)

Genotype
AA AB AC BB BC CC CD
Affected 0 0 5 0 12 1 0
Normal 6 12 1 2 0 0 1

2. Your research group is working with a recessive human disease located on a somatic chromosome. You have identified a specific probe/enzyme combination that you feel may be useful as a molecular marker. Below is a pedigree showing the parents and offspring. Affected individuals are represented as filled in male or female symbols. The RFLP patterm for each parent and offspring is given below the individual.

1. Is this marker system exhibiting linkage to the disease? What information did you use to make your decision?
2. Which allele is linked to the disease?
3. Do any of the offspring carry a recombinant chromosome?
4. Using the Lod method, determine an optimum distance between the marker and the gene. Calculate the Lod score using at least three different theta values.(10 pt)