Question

A $340$ ${}^{\circ }A$ long segment of DNA molecule has $20$ thymine nitrogenous bases, what will be the number of guanine nitrogen bases in the same segment?

• A. $10$
• B. $40$
• C. $80$
• D. $160$

Answer 1

The correct option is C $80$

Length of one base pair = 3.4 $\stackrel{\circ }{A}$

If the segment of DNA has 20 thymine bases, then it will have 20 adenine bases (as A-T is formed in DNA).

So, the length covered by 20 thymine base = 20 X 3.4 = 68 $\stackrel{\circ }{A}$

The length covered by G-C will be 340 - 68 = 272 $\stackrel{\circ }{A}$

So, the number of guanine will be 272/3.4 = 80

Thus the correct answer is option C.