Explain how a DNA molecule is arranged
Genes are made of a chemical called DNA, which is short for 'deoxyribonucleic acid'. The DNA molecule is a double helix: that is, two long, thin strands twisted around each other like a spiral staircase.The DNA double helix showing base pairs. The sides are sugar and phosphate molecules. The rungs are pairs of chemicals called 'nitrogenous bases', or 'bases' for short.There are four types of base: adenine (A), thymine (T), guanine (G) and cytosine (C). These bases link in a very specific way: A always pairs with T, and C always pairs with G. The DNA molecule has two important properties.he rungs are pairs of chemicals called 'nitrogenous bases', or 'bases' for short. There are four types of base: adenine (A), thymine (T), guanine (G) and cytosine (C). These bases link in a very specific way: A always pairs with T, and C always pairs with G. The DNA molecule has two important properties.