2. You are an evolutionary biologist studying Keratin expression in hair and you

Question

2. You are an evolutionary biologist studying Keratin expression in hair and you wonder which differences, on the molecular level, might have influenced the loss of body hair in humans, relative to other apes. You decide to sequence a locus on chromosome 12 (several Keratin genes are there), and realize that among several SNPs, there is a mutation resulting in the premature termination codon in KRTAP-1 gene exon 4 in human genome, relative to gorilla's and chimp's sequence. This SNP results in a truncated, non-functional protein, which may hold a clue to your inquiry. However, the sequence results indicate that the premature codon termination only cuts out 9 subsequent AAs. You decide to PCR-amplify and subclone gorilla, chimp, and human KRTAP-1 into a vector and explore genotype-phenotype relationships of this keratin-associated protein expressed in hair. After "successful" subcloning and cutting out/ purifying the PCR product of all three biological samples, you are determined to verify your results on the gel: a) What experimental adjustments could you make relative to your gel electrophoresis to increase your chances of resolving the PCR product size differences among these 3 PCR products? Note that the exon 4 chimp/gorilla insert is about 1.4 Kb. (5 pts)

Explanation / Answer

Let's see the difference in terms of base pairs. The difference comes from 9 amino acids hence 27 bp. So to resolve the differences we need a high strength gel. High strength will ensure more cross linking and hence more resistance thus thus more resolution. It will be able to differentiate small bp differences amobg the sample. Further we use polyacrylamide gel which resolve as small as 5bp differences. We use appropriate ladder to help us quantify the size difference.

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