Final answer:
DNA is composed of two antiparallel strands of nucleotides that form a double helix, with the backbone made of sugar and phosphate and paired nitrogenous bases (A-T and G-C) on the inside, connected by hydrogen bonds.
Step-by-step explanation:
DNA Structure Overview
The structure of DNA consists of two long chains of nucleotides twisted into a double helix. Each nucleotide is made up of a 5-carbon sugar known as deoxyribose, a phosphate group, and a nitrogenous base. The sugar and phosphate form the backbone of the DNA, running along the outside of the helix, while the nitrogenous bases are inside, paired with each other. Specifically, adenine (A) pairs with thymine (T), forming two hydrogen bonds, and guanine (G) pairs with cytosine (C), forming three hydrogen bonds. These base pairs create ladder-like rungs between the two DNA strands which are held together by covalent bonds between the sugar of one nucleotide and the phosphate of another. The strands run in opposite directions, with one strand starting at the 5' end and the other at the 3' end, a configuration described as antiparallel.