For a double strand DNA, one strand is given below:
The amount of energy required to split the double strand DNA into two single strands is _____ kcal mol.
[Given: Average energy per H-bond for A-T base pair kcal mol, G-C base pair kcal mol, and A-U base pair kcal mol. Ignore electrostatic repulsion between the phosphate groups.]
The given strand -AGTCACGTAAGTC- has nucleotides. Its complementary strand reads -TCAGTGCATTCAG- (replacing each base with its Watson–Crick partner: A↔T, G↔C). DNA contains no uracil, so the A-U energy is irrelevant.
Count base pairs in the duplex:
A-T pairs: positions with A or T on the given strand. Reading the sequence A, G, T, C, A, C, G, T, A, A, G, T, C, the A and T bases together number (four A's and three T's), giving A-T pairs.
G-C pairs: the remaining positions hold G or C ( G's and C's), giving G-C pairs.
Hydrogen bonds per pair: A-T pair has H-bonds; G-C pair has H-bonds.
Total energy to separate the two strands:
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