Question

What peptide would you expect to result from a 21-nucleotide-long DNA sequence that contains only the base adenine? (Hint: Your first step should be to convert the DNA codon to a corresponding mRNA codon.)

a peptide composed of 7 phe
a peptide composed of 21 phe
a peptide composed of 7 lys
a peptide composed of 21 lys

Answer 1

A peptide composed of 7 Phe.

Here is how:1. Converting Adenine of DNA into mRNA would give you 21 nucleotides of Uracil (because no thymine in RNA)

2. 3 nucleotides make up one codon for a polypeptide. So 21/3 = 7. So 7 of the same polypeptide.

3. Looking at an mRNA codon --> UUU codes for the amino acid Phe.

That is how I came to the answer