The following ratio is generally constant for a given species :-
- A+CT+G
- G+CA+T
- A+GC+T
- T+CG+A
Answer
(2) G+CA+T
Solution
As per Chargaff's rule, in double-stranded DNA A = T and G = C.
So A+GC+T, A+CT+G and T+CG+A are all equal to 1 in every organism and do not characterise a species.
The ratio G+CA+T, on the other hand, differs from species to species but is constant for a given species.
Answer: (2)