DNA Structure

DNA has a double helix shape, which is like a ladder twisted into a spiral. Each step of the ladder is a pair of nucleotides. Nucleotides are molecules made of deoxyribose, a sugar with 5 carbon atoms, and a phosphate group made of phosphorus and oxygen, and nitrogenous base. There are four types of nucleotide: Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). The DNA ladder is made of two bases, one base coming from each leg. The bases connect in the middle: 'A' only pairs with 'T', and 'C' only pairs with 'G'. The bases are held together by hydrogen bonds. Adenine (A) and thymine (T) can pair up because they make two hydrogen bonds, and cytosine (C) and guanine (G) pair up to make three hydrogen bonds.

DNA Strand