ABSTRACT

Deoxyribonucleic acid (DNA) is the genetic molecule of all cellular organisms and DNA viruses. DNA exists in every cell in the human body; it is localized predominantly to the nucleus, and contains all the molecular information needed for replication, transcription, and translation. The DNA molecule consists of two strands of nucleotides which form the double-helix structure. The two strands are composed of four DNA nucleotides and complement each other: adenine (A) forms two hydrogen bonds with thymine (T) and cytosine (C) forms three hydrogen bonds with guanine (G). The human genome contains 3.2 billion nucleotides arranged in 22 pairs of autosomal chromosomes (chromosomes 1-22), and two sex chromosomes (X and Y). Both female and male genomes contain the 22 pairs of autosomal chromosomes, but the female genome contains a pair of X chromosomes, and the male genome contains one copy of the X chromosome and one copy of the Y chromosome. The chromosomes differ in sequence, gene content, size, and structure.