The average energy of each hydrogen bond in A-T pair is x kcal `mol^(-1)` and that in G-C pair is y kcal `mol^(-1)`. Assuming that no other interaction exists between the nucleotides, the approximate energy required in kcal `mol^(-1)` to split the following double stranded DNA into two single strands is

[each dashed line may represent more than one hydrogen bond between the base pairs ]

Options

A. 10x+9y
B. 5x+3y
C. 15x+6y
D. 5x+4.5y

Answer

A

Explanation

Number of H-bond is A-T pair=2, while no of H-bond in G-C pair is 3. Therefore
(i) Total number of A-T. H-bond= number of A-T pair `xx` Number of H bond `=5xx2=10`
(ii) Total number of G-C H-bond = number of G-C pair `xx` number of H bond `=3xx3=9`
Total energy required to dissociate the stand =10x+9y kcal `mol^(-1)`