Question

In a DNA segment of six coils, $22\text{bp}$ are linked by two hydrogen bonds. How many cytosine bases would be present?

• A. $76$
• B. $22$
• C. $38$
• D. $44$

Answer 1

The correct option is C $38$

Number of cytosine bases
One complete turn or coil of a DNA helix has $10$ base pairs.
Therefore $6$ coils have $60$ base pairs.
Of these, $22$ base pairs are linked by double hydrogen bonds, i.e, these $22$ are A-T base pairs.
Therefore, the remaining $38$ base pairs are G-C pairs.
Thus, the number of cytosine bases present $=38$