Question

question 1 of 25

which sentence describes a substitution error that could occur during dna replication?

a. a cytosine is added where an adenine is supposed to be in the growing strand.
b. a cytosine is left off the growing strand where a cytosine was supposed to be added.
c. a cytosine is added to the template strand when it was supposed to be added to the growing strand.
d. two cytosine bases are added where a single cytosine was supposed to be in the growing strand.

Explanation:

Define substitution mutations

A substitution mutation is a type of replication error where one nucleotide base is replaced by another. In Gene Mutations, this means a single incorrect base is incorporated into the newly synthesized strand in place of the correct base.

Analyze the given options

• Option A: "A cytosine is added where an adenine is supposed to be in the growing strand." This describes replacing one base (adenine) with another (cytosine), which is a substitution.
• Option B: "A cytosine is left off..." This describes a deletion error.
• Option C: "A cytosine is added to the template strand..." Replication adds bases to the growing strand, not the template strand.
• Option D: "Two cytosine bases are added..." This describes an insertion error.

Identify the correct choice

Based on the definitions of DNA Replication Errors, replacing one base with another is a substitution. Therefore, Option A is the correct description.

Answer:

• (A) A cytosine is added where an adenine is supposed to be in the growing strand. (Correct answer)
• (B) A cytosine is left off the growing strand where a cytosine was supposed to be added.
• (C) A cytosine is added to the template strand when it was supposed to be added to the growing strand.
• (D) Two cytosine bases are added where a single cytosine was supposed to be in the growing strand.