Question

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion? PLEASE EXPLAIN YOUR ANSWER!
A.single-stranded genomes always have a large percentage of purines
B.using the formula: G � A = C + T
C.Double-stranded genomes have equal amounts of A and T
D.Single-stranded genomes have a higher rate of mutation

Answer 1

Answer:

The correct answer is option C. "Double-stranded genomes have equal amounts of A and T".

Explanation:

According to Chargaff's rules, double-stranded genomes have equal amounts of guanine and cytosine, and equal amounts of adenine and thymine. This rule comes from the specific base pairing among nucleotides, where in normal conditions guanine only establishes a binding with cytosine and adenine only binds with thymine. Therefore, this rule only applies to double-stranded genomes. Since the viral strains have no equal amounts of guanine and cytosine and equal amounts of adenine and thymine, the viral strains could not be double-stranded but single-stranded.