Answer to Question 4 from November, 2005

Please name a disease that is caused by a mutation in a gene that affects DNA repair. For the disease that you named, list the gene or genes in which mutations can cause the disease. For any one of the genes in your list, explain (in no more than two sentences) the function in DNA repair of the protein encoded by the gene (5 points).

There were many possible answers to this question. I gave full credit for answers that provided the following:

1. The correct name of a human genetic disease involving defects in DNA repair. I accepted abbreviations for disease names. Thus possible answers included HNPCC, XP, XP-V, CS, TTD, ATLD and NBS.
2. The correct list of all the genes, which, when mutated, could give rise to the disease. In the case of XP, the list is a long one. It includes XPA, XPB, XPC, XPD, XPF, and XPG.
3. A brief explanation (one or two sentences) of the function of the gene product in DNA repair. I did not consider the simple statement that gene product X is important for DNA repair to be a sufficient answer. You needed to name the repair pathway (for example, NER) and you needed to describe the specific role in repair of the gene product you chose (for example, "unwinding DNA strands to provide access to nucleases").

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