In case of double-stranded DNA, which of the following base ratios are equal to one ? (1) ( G + T ) /( A + C ) (2) ( A + G ) /( C + T ) (3) C / G (4) ( A + T ) /( G + C )

Question

In case of double-stranded DNA, which of the following base ratios are equal to one ? (1) ( G + T ) /( A + C ) (2) ( A + G ) /( C + T ) (3) C / G (4) ( A + T ) /( G + C ) (A) 1, 2 and 3 are correct (B) 1 and 2 are correct (C) 2 and 4 are correct (D) 1 and 3 are correct

Tardigrade Admin · Accepted Answer

Chargaff (1950) discovered the equivalence rule, which suggested that despite wide compositional variations exhibited by different types of DNA, the total amount of purines equals to the amount of pyrimidine (A+G=T+C). The amount of adenine equals to the amount of thymine (A=T) and the amount of guanine equals to the amount of cytosine ( G = C ) . In contrast, the ( T + A / G + C) ratio varied widely in DNAs of different species. In case of double-stranded DNA ( A + G ) /( C + T ) C / G and ( G + T ) /( A + C ) ratios are always or almost equal to one.

Q. In case of double-stranded DNA, which of the following base ratios are equal to one ? (1) (G+T)/(A+C) (2) (A+G)/(C+T) (3) C/G (4) (A+T)/(G+C)

1, 2 and 3 are correct

1 and 2 are correct

2 and 4 are correct

1 and 3 are correct

Q. In case of double-stranded DNA, which of the following base ratios are equal to one ?
(1) $(G + T) / (A + C)$
(2) $(A + G) / (C + T)$
(3) $C / G$
(4) $(A + T) / (G + C)$