Below are sequences of part of a gene taken from three species of plants.
Plant A: AGATCTACGCGCAGTTTC
Plant B: AGATTGGCGCAGTATC
Plant C: AGATTAGGCGCAGTTTC
Align the sequences.If each added gap required to align the sequences represents two nucleotide differences, how many differences are between species A and species B?

Question

Below are sequences of part of a gene taken from three species of plants. 
Plant A: AGATCTACGCGCAGTTTC
Plant B: AGATTGGCGCAGTATC
Plant C: AGATTAGGCGCAGTTTC
Align the sequences.If each added gap required to align the sequences represents two nucleotide differences, how many differences are between species A and species B?

Quizplus · Accepted Answer

To align the sequences, we can insert gaps as shown below:
Plant A: AGATCTACGCGCAGTTTC
Plant B: AGATTGGCGCAGTATC
Plant C: AGATTAGGCGCAGTTTC

Aligned sequences:
AGATCTACGCGCAGTTTC
AGATTGGCGCAGTATC-
AGATTAGGCGCAGTTTC

To calculate the number of differences between species A and B, we count the number of non-gaps that are different between the two sequences. There are four differences:
- ATCTACGCGC vs ATTGGCGCAG (difference at positions 5-14)
- T vs A (difference at position 17)

Each added gap represents two nucleotide differences, so the final answer is C) Four.

Below Are Sequences of Part of a Gene Taken from Three