If Adenine makes 30% of the DNA molecule, what will be the percentage of Thymine, Guanine and Cytosine in it?

Options

A. T : 20 , G : 20 , C : 30
B. T : 30 , G : 20 , C : 20
C. T : 20 , G : 25 , C : 25
D. T : 20 , G : 30 , C : 20

Answer

B

Explanation

According to Chargaff. s nitrogen base pairing rule for a double stranded DNA, which states that amount of Adenine is equal to Thymine and Guanine is equal to Cytosine
Here [A] = [T] , `because [A]= 30% implies [T] = 30%`
`because [A] + [T] + [C] + [G] = 100`
`implies [C] + [G] = 100 - [A] - [T]`
`implies [C] + [G] = 100 - 30 - 30 = 40%`
`implies C= G = 20`% each [`because [C] = [G]`]
Thymine[T]=30%, Guanine[G]=20%, Cytosine[C]= 20%.