1) What is the name of the type of mutation that results in the S allele? 2) Spe

Question

1) What is the name of the type of mutation that results in the S allele? 2) Specifically, what is the impact of that mutation the resulting hemoglobin polypeptide? (refer to the amino acid table at the end of the exam) 3) What impact does this have on the function of the resulting S hemoglobin polypeptide, and its ability to bind O2? 4) Which is the best genotype in an environment in which malaria is NOT present, and why? 5) Which is the best genotype in an environment in which malaria IS present, and why?

Explanation / Answer

1) Mutation is a heritable change in genetic information. It can be caused by base substitution (which alters a single codon), base insertion or deletion (which alters the reading frame and may change many codons). If we consider A allele as the original DNA sequence then in S allele transversion (Purine is replace by a pyrimidine) type of base substitution occurs as A (Purine) is replace by T (Pyrimidine). Now, base substitution can cause missense mutation (New codon encodes a different amino acid), nonsense mutation (New codon is a stop codon & premature termination of translation occurs) & silent mutation (New codon encodes same amino acid). In our case valine is produced in place of glutamine. So, in S allele missense mutation occurs.

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