A segment of DNA from a lab mouse is determined to be 5’ – GGATCCTCATG – 3’. Which of the following DNA segments would be the result of this original DNA sequence experiencing both a point mutation and a deletion?
A) 5’ – GCATCCTCATG – 3’
B) 5’ – TGATCCCAG – 3’
C) 5’ – GGTCCTCATC – 3’
D) 5’ – GGATCCATG – 3’
Explanation
A point mutation is one in which a single DNA base has be replaced by another and a deletion in one in which a single DNA base has been deleted. The question asks us to look for an answer choice that has had both a point mutation and a deletion. Only choice (C) matches these requirements.
A) 5’ – GCATCCTCATG – 3’
B) 5’ – TGATCCCAG – 3’
C) 5’ – GGTCCTCATC – 3’
D) 5’ – GGATCCATG – 3’
A, D: Neither (A) nor (D) has had any deletions at all – the length of the DNA chain is unchanged.
B: Two deletions have occurred as well as a point mutation. Both the 7th and 10th nucleotide are missing (both T).
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