Question

A. Bacteriophage MS2 carries its genetic information in RNA. Its chromosome is analogous to a polygenic molecule of mRNA in organisms that store their genetic information in DNA. The MS2 mini-chromosome encodes four polypeptides (i.e., it has four genes). One of these four genes encodes the MS2 coat protein, a polypeptide 129 amino acids long. The entire nucleotide sequence in the RNA of MS2 is known. Codon 112 of the coat protein gene is CUA, which specifies the amino acid leucine. If you were to treat a replicating population of bacteriophage MS2 with the mutagen 5-bromouracil, what amino acid substitutions would you expect to be induced at position 112 of the MS2 coat protein (i.e., Leu —> other amino acid)? (Note: Bacteriophage MS2 RNA replicates using a complementary strand of RNA and base-pairing like DNA.)

b.Would such mutations occur if a non-replicating suspension of MS2 phage was treated with 5-bromouracil?

Answer 1

Aspartate (CUG)

Explanation:

5-bromouracil is a base analog that can induce mutations in the DNA strand by causing mispairing in replication. The 5-bromouracil can pair with adenine or guanine in template DNA, and therefore, in this case, can produce a mutation in the codon that encodes for CUA (Lys) to CUG (Asp)