Blueprint MCAT Formerly Next Step
Return to Blog Homepage

PCAT Biological Processes – DNA Mutation and Deletion

  • by Sam
  • Oct 24, 2017
  • PCAT Question of the Day

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’ – GGATCCCAG – 3’

C) 5’ – GGTCCTCATC – 3’

D) 5’ – GGATCCATG – 3’

 

Explanation

A point mutation is one in which a single DNA nucleotide has been replaced by another, and a deletion DNA nucleotide has been deleted.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’ – GGATCCCAG – 3’

C) 5’ – GGTCCTCATC – 3’

D) 5’ – GGATCCATG – 3’

A: Answer choice A contains a point mutation that replaced a guanine (G) with a cytosine (C), but it does not contain a deletion.

B: Two thymine deletions have occurred (at the 7th and 10th positions), but there are no point mutations.

D: Thymine and cytosine have been deleted at the 7th and 8th positions, respectively, but there are no point mutations.

Submit a Comment