The genome is the entire set of genetic instructions found in a cell. In humans, the genome consists of 23 pairs of chromosomes, found in the nucleus, as well as a small chromosome found in the cells' mitochondria. Each set of 23 chromosomes contains approximately 3.1 billion bases of DNA sequence.


"Genome" is a funny word. Nobody can figure out how to pronounce it. Is it "jeh-NOHM" or "JEE-nohm"? I've heard various opportunities for mispronunciations, some of which are pretty funny. But basically, it is the entire instruction set of an organism; all of the DNA. For humans, that amounts to about 3.1 billion letters of the code--As, Cs, Gs, and Ts--all in the right order, spread across all of those chromosomes.

- Francis S. Collins, M.D., Ph.D.