Question

Draw the chemical structure of a dinucleotide composed of A and G, labeling the 5' and 3' ends. Opposite this structure, draw the dinucleotide composed of T and C in an antiparallel (upside-down) orientation, labeling the 5' and 3' ends. Indicate the hydrogen bonds that will form between paired bases.

Answer 1

A dinucleotide composed of adenine (A) and guanine (G) pairs with an antiparallel dinucleotide composed of thymine (T) and cytosine (C), with A forming two hydrogen bonds with T and G forming three hydrogen bonds with C.

Step-by-step explanation:

The chemical structure of a dinucleotide composed of adenine (A) and guanine (G) has a phosphate backbone with the 5' end starting at the phosphate group of a 5' carbon of a deoxyribose sugar and the 3' end at the 3' carbon of the deoxyribose sugar. The dinucleotide composed of thymine (T) and cytosine (C), drawn antiparallel to the AG dinucleotide, starts with the T at the 3' end and ends with the C at the 5' end.

In between these bases, hydrogen bonds form with A pairing with T via two hydrogen bonds, and G pairing with C via three hydrogen bonds, consistent with the DNA base-pairing rules. The 5' end of one nucleotide is linked to the 3' end of another nucleotide by a phosphodiester bond, forming a double helix structure. For the final answer in two lines: The AG dinucleotide pairs with the TC dinucleotide in an antiparallel fashion, with A paired to T with two hydrogen bonds and G paired to C with three hydrogen bonds.