Question

question 44
1 pts
a scientist uses polymerase chain reaction (pcr) to compare the sequence of a disease and a healthy gene. the scientist finds that these two genes are identical except for one g in place of a t at position 256 in the gene. this type of mutation is a(n)
insertion.
deletion.
substitution mutation.
silent mutation.

Explanation:

• Insertion mutation: involves adding one or more nucleotide base pairs into a DNA sequence. Here, it's a replacement, not an addition, so this is incorrect.
• Deletion mutation: means removing one or more nucleotide base pairs from a DNA sequence. This is a substitution, not a deletion, so this is wrong.
• Substitution mutation: occurs when one nucleotide is replaced by another. In the problem, a G replaces a T at a specific position, which fits the definition of substitution mutation.
• Silent mutation: is a type of substitution mutation where the change in nucleotide does not change the amino - acid (due to the degeneracy of the genetic code). But the question does not mention anything about the effect on the amino - acid (if it's silent or not). However, based on the nucleotide - level description (one nucleotide replacing another), substitution mutation is the most appropriate category at the DNA - sequence level.

Answer:

substitution mutation.