Question

A DNA segment has base order CCC ATA GCT. Which copy exhibits a deletion in the first codon triplet and then a substitution mutation? (1 point)
O CCA TAG CT
0 CCC TAG CT
О ССА ТАА СТ
O CCA ATA GCT

Answer 1

To determine which copy exhibits a deletion in the first codon triplet (CCC) and then a substitution mutation, let's analyze each option.

The original base order is: **CCC ATA GCT**.

1. **Option A: CCA TAG CT**
- First codon has a deletion (C [removed] → CA), so there is a deletion here.
- The second codon has a change from ATA to TAG (substitution mutation).

2. **Option B: CCC TAG CT**
- No deletion in the first codon; it remains CCC. Additionally, no substitution has occurred in the subsequent codons.

3. **Option C: CCA TAA CT**
- The first codon has a deletion (C [removed] → CA). However, this doesn't show a substitution in the second codon because it stays the same as TAA (a point mutation).

4. **Option D: CCA ATA GCT**
- There is a deletion in the first codon (C [removed] → CA) but no substitution in the second codon (ATA).

After analyzing these options, **Option A (CCA TAG CT)** is the correct one, as it reflects a deletion in the first codon (CCC to CCA) and a substitution mutation (ATA to TAG).