Question

Assume that the molar percentage of thymine in a double stranded DNA is 20. What are the percentages of the four bases (G, C, T, A)?

b. The base content of a sample of DNA is as follows: A=31% G=31% T=19% C=19%. What conclusion can be drawn from this information?

Answer 1

(a) in a double stranded DNA , amount of Adenine is always equal to Thymine & amount of Guanine is always equal to amount of Cytosine, according to the Chargaff rule.

So T= A i.e, T = A = 20 %

Now A&T consumes 40 % of total amount.

So out of rest 60 %, 30% will Guanine and 30% will be Cytosine. i.e., G=C= 30%.

(b) now as given is the question., A is not equal to T & also G is not equal to C. Means that it is not following chargaff rule. So it must be a single stranded nucleic acid or it could be a primer.