A genome is the complete set of genetic information for an organism. This can be a single cell or the entire organism. The term “genome” was first coined in 1966 by American biologist and geneticist Walter F. Bodmer.
The human genome contains approximately 3 billion base pairs of DNA, which are organized into 24 distinct chromosomes. Each chromosome contains many genes, which are the basic units of hereditary information. Genes are made up of DNA, and they encode the instructions needed to build proteins. Proteins perform many essential functions in the body, such as enzymes that catalyze chemical reactions, structural proteins that form tissues, and hormones that regulate metabolism.
The sequence of base pairs in a gene determines the amino acid sequence of a protein. Changes in the DNA sequence (called mutations) can alter the protein produced by a gene, which can lead to changes in an organism’s phenotype (physical appearance and/or function). Some mutations have no effect on an organism; others may cause disease or death.
Most genomes consist of both coding and non-coding regions. Coding regions are those that contain the instructions for making proteins (or other functional RNA molecules). Non-coding regions do not code for proteins; instead, they may play a role in regulating gene expression or provide structure for chromosomes. The human genome also includes numerous pieces of so-called “junk DNA” that do not seem to serve any purpose at all.
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