J Deen has a family history of colon cancer consistent with

J. Deen has a family history of colon cancer consistent with hereditary non-polyposis colorectal cancer (HNPCC),an autosomal dominant form of colon cancer. Mutations in a family of genes, specifically MSH2 or MLH1, are involved in DNA repair have been linked to HNPCC. Your lab received Mr. Deen’s blood sample and has manually sequenced the MSH2 gene. The gel below shows the section of the sequence where you found a mutation.For comparison, a wildtype (known to be normal) individual is also sequenced. The two gels are as follows

Wid type (a) What is the mutation observed in J. Deen? How confident are you based on the gel above What could you do to confirm this observation (b) Does the mutation alter the protein sequence? How?

Solution

a)Mutation observed in J.Deen is in the MSH2 gene which is a tumor suppressor gene that codes for a protein essentially functioning in DNA repair process.Mutation in this gene results in occurence of cancer.The gel above shows the results of sequenced MSH2 gene from wild and mutant type and we can see a a specific band is missing in the mutant type in lane A but is present in wild type lane A. i.e 2nd band in lane A of wild and mutant type.To confirm this observation we can conduct a real time PCR.

b) Yes, the mutation will alter the protein sequence as the missing sequence /mutated sequence will not encode the corresponding correct aminoacid and a mutated protein will be formed.