Question

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

• A. T : 20 ; G : 30 ; C : 20
• B. T : 20 ; G : 20 ; C : 30
• C. T : 20 ; G : 25 ; C : 25
• D. T : 30 ; G : 20 ; C : 20

Answer 1

The correct option is D

T : 30 ; G : 20 ; C : 20

The correct option is D:

Explanation of the correct option:

1. The hereditary material in an organism is carried by DNA. It is a form of polyfunctional nucleic acid. A nitrogenous base (purine and pyrimidine), a pentose sugar, and a phosphate make up nucleotides.
2. Nucleotides are made up of nitrogenous bases like:
   1. Adenine and Guanine are purines.
   2. Cytosine and thymine are pyrimidines.
3. The nucleotides are present in a 1:1 ratio, according to Chargaff's rule.
4. Adenine always bonds or pairs with Thymine, while Guanine always bonds or pairs with Cytosine.
5. The percentage of Adenine, which is 30%, is already known. As a result, Thymine's percentage rises to 30%.
6. Adenine and Thymine account for 60% of the total, with the remaining 40% split evenly between Cytosine and Guanine. i.e. each receives 20%.

Final answer: If Adenine makes 30% of the DNA molecule, then the percentage of Thymine, Guanine and Cytosine in it will be 30%, 20% and 20% respectively.