Question

A DNA segment has base order TCG TAT AAC. Which copy exhibits an insertion mutation without a frameshift?(1 point)
Responses

TCC TAT AAC
TCC TAT AAC

TCG TAT AC
TCG TAT AC

TCG TAT GAAC
TCG TAT GAAC

TCG CCG TAT AAC

Answer 1

To determine which copy exhibits an insertion mutation without a frameshift, we need to understand how mutations can affect the DNA sequence.

A **frameshift mutation** occurs when nucleotides are added or removed from the DNA sequence in a number that is not a multiple of three, which shifts the reading frame of the sequence. An **insertion mutation** that does not cause a frameshift would involve the addition of nucleotides in multiples of three.

The original sequence is:
**TCG TAT AAC**

Now, let's analyze the given options:

1. **TCC TAT AAC** - This is a substitution mutation, not an insertion.

2. **TCG TAT AC** - This sequence has one nucleotide deleted, which is not an insertion.

3. **TCG TAT GAAC** - This sequence has "GA" inserted between "TAT" and "AAC." Since "GA" is 2 nucleotides, it adds a non-multiple of three, which causes a frameshift.

4. **TCG CCG TAT AAC** - This sequence adds "CCG" before "TAT." Since "CCG" is 3 nucleotides long, this is a valid insertion mutation that does not change the reading frame.

Based on this analysis, the correct answer is:
**TCG CCG TAT AAC**