42. Which of the following base pairs could proteins distinguish, and why? a. Major groove base pairs (GC/CG, AT/TA, GC/TA, GC/AT) b. Minor groove base pairs (GC/CG, AT/TA, GC/TA, GC/AT)

Major groove - AT/TA.

Minor groove - GC/CG.

Explanation:

The most common form of the DNA is B DNA that are present in the living organism. Two main types of groove that are present in DNA is major groove and minor groove. The major groove is wider and minor groove is narrower.

The major groove contains AT/TA base pairing and mainly present at the site in which the base pairs are far apart and wider due to the steric hindrance. The minor groove contains contain  GC/CG and mainly occurs at the site where back bone are close with each other.

Thus, the answer is Major groove - AT/TA.

Minor groove - GC/CG.