Question

How many hydrogen bonds would be there in a stretch of dsDNA having 19% cytosine if the total number of base pairs is 1000?
[0.7 mark]

• A. 1310
• B. 2620
• C. 2380
• D. 1690

Answer 1

The correct option is C 2380

Since number of base pairs = 1000
Total number of bases $=2\times 1000=2000$
Number of cytosine = Number of guanine $=2000\times \frac{19}{100}=380$
Number of adenine = Number of thymine$=\frac{2000}{2}-380=620$
There are three hydrogen bonds between cytosine and guanine and two hydrogen bonds between adenine and thymine. Therefore, total number of hydrogen bonds in the given stretch of $DNA=3\times 380+2\times 620$
$=1140+1240=2380$.