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WBCS Preliminary Examination 2015 — General Studies · Question 180 of 200

Q180
General ScienceBiology
One turn of DNA helix measures
  1. a.$34A°$
  2. b.$3.4A°$
  3. c.$24A°$
  4. d.$44A°$

Answer: (A) $34A°$

In the B-form double helix DNA (the most common form in cells), one complete turn of the helix spans 10 base pairs. Each base pair is separated by 3.4 Å (Angstroms), so one complete turn = $10 \times 3.4 = 34$ Å. The option $34A°$ represents 34 Angstroms.

Q179 Whole paperQ181