Question

If a linear double stranded DNA with 1000 base pairs have A = 15%, then find out total number of hydrogen bonds in between the two strands of this DNA?

• A. $6000$
• B. $600$
• C. $2700$
• D. $2100$

Answer 1

The correct option is C $2700$

Answer (3)
[A] + [G] = 50% (Chargaff's rule)
So, [G] = [50 $-$ 15] % = 35%
[A = [T] = 15% $\Rightarrow$ [A] + [T] = 30%
So, number of [A] + [T] = $1000\times \frac{30}{100}=300$
Because two hydrogen bonds are present in between adenine and thymine, So number of hydrogen bonds = 300 × 2 = 600
Similarly, [G] + [C] = [100 $-$ 30] = 70%
So, number of [G] + [C] $=100\times \frac{70}{100}=700$
Three hydrogen bonds are present between G and C, so number of hydrogen bonds $=700\times 3=2100$
So, total number of hydrogen bonds $=2100+600=2700$