Question

In one polynucleotide strand of a DNA molecule, the ratio of A+T/G+C is 0.3. What is the A+G/T+C ratio of the entire DNA molecule?

• A. 1
• B. 0.3
• C. 0.7
• D. 1.2

Answer 1

The correct option is A 1

A + T/G + C ratio is species specific and here it is mentioned to be 0.3.

A + G/T + C (Purines/Pyrimidines) is the ratio which is constant for all double-stranded DNA and its value is 1.

This is because in a double-stranded DNA, adenine always pairs with thymine. So, the amount of A (adenine) is equal to the amount of T (thymine).

Guanine always pairs with cytosine. So, the amount of C (cytosine) is equal to the amount of G (guanine).

Therefore, the amount of purines will always be equal to the amount of pyrimidines according to Chargaff's rule.

Hence, A + G/T + C = 1.