Question

BIOCHEM: Draw an AT and a GC Watson-Crick base pair.

Please explain, thank you.

Answer 1

Ans. Hydrogen bond is a weak attractive force between a highly electronegative atoms (O, N, F) and a H-atoms linked to such atoms.

The criteria for H-bonds formation is that there must be -

I. A highly electronegative atom (F, N, O-atom), and

II. A H-atoms linked to such atoms (F, N, O).

# AT Base pairing: There are two H-bonds between AT bases-

            Between N-atom of C1-amine group adenine and C4 O-atom of thymine

            Between N-atom of adenine ring and N-atom of thymine ring.

# GC bases form three H-bonds as follow-

Between O-atom on C6 of guanine and H-atom on C4 amine of cytosine.

Between H-atom of N1 of guanine ring and N3-atom of cytosine ring.

Between H-atom on C2-amine group of guanine and O-atom on C2 of cytosine.