Question

How many hydrogen bonds exist between this DNA strand and its complementary strand?

5'-GGAAGAC-3'

Answer 1

There are three hydrogen bonds between a guanine and cytosine and two hydrogen bonds between an Adenine and thymine.

The complementary strand should have the corresponding nucleobase to bind to DNA strand i.e, for G it should have C, for C <---> G, A <---> T and A <---> T.

Since, the given structure has 3 G and a C, it should account for 4 x 3 = 12 hydrogen bonds.

It also has 3 A's, i.e., 3 x 2 = 6 hydrogen bonds.

Therefore, there are 12 + 6 = 18 hydrogen bonds.