In DNA fragment, there are 8 turns with
40% of bases are cytosines . What
would be the total number of Hydrogen Bonds present in this DNA fragment.???

40 % cytosine 

40 % Guanine

10 % Adenine

10% Thymine 

Now we know, 10 base pairs are present in each turn. so 8 turns would have total of 80 base pairs.

out of 80, 80% are  Cytosine - Guanine and the rest 20% are Adenine - Thymine

80 % of 80 = 64 

1 Cytosine - Guanine has 3 hydrogen bonds, so 64 Cytosine - Guanine will have 192 hydrogen bonds

20 % of 80 = 16

1 Adenine - Thymine has 2 hydrogen bonds, so 16 Adenine - Thymine will have 32 hydrogen bonds

Total hydrogen bonds = 224

:P