A particular protein has the amino acid sequence: . . . Ala-Pro-His-Trp-Arg-Lys-Gly-Val-Thr . . within its primary structure. A geneticist studying mutations affecting this protein discovered a mutant that produced a shortened protein molecule that terminated within this region. In this mutant protein, the His became the last amino acid. What DNA single-base change(s) would cause the protein to terminate at the His residue

The correct answer is - nonsense mutation.

Explanation:

The given amino acid sequence  Ala-Pro-His-Trp-Arg-Lys-Gly-Val-Thr of a particular protein is affected by a mutation that leads to the shortened protein that ends in this region only. As we know the His amino acid becomes the last amino acid so in such case is it takes place due to nonsense mutation that is the only mutation or change result to terminate before or at the His codon.

The Trp codon which is coded by UGG codon could have been changed to either a UAG or a UGA codon in this case.

The correct answer is - nonsense mutation.