The average energy of each hydrogen bond in A - T pair is x kcal mol - 1 and that in G - C pair is y kcalmol - 1 . Assuming that no other interaction exists between the nucleotides, the approximate energy required in kcalmol - 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]

Step-by-step solution

Number of H -bonds in each A - T pair = 2 Number of H -bonds in G - C pair = 3 . The given double stranded DNA has 5 A - T and 3   G - C pairs. ∴ Total number of H -bonds in 5   A - T pair = 5 × 2 = 10 Total number of H-bonds in 3   G - C pair = 3 × 3 = 9 ⇒ Average energy of 10 H -bonds in A - T pair = 10 x . Average energy of 9 H -bonds in G - C pair = 9 y Thus, the approximate energy required to split the double stranded DNA in two single strands = 10 x + 9 y