Human Genome

Human Genome

The human (Homo sapiens) genome is the complete set of human genetic information, stored as DNA sequences within the 23 chromosome pairs of the cell nucleus, and in a small DNA molecule within the mitochondrion. The haploid human genome (contained in egg and sperm cells) consists of three billion DNA base pairs, while the diploid genome (found in somatic cells) has twice the DNA content. Although the human genome has been completely read by DNA sequencing, it is not yet fully understood. Many (though probably not all) genes have been identified, yet much work still needs to be done to completely elucidate the biological functions of their protein and RNA products. Recent results indicate that most of the vast quantities of noncoding DNA within the genome have associated biochemical activities, including regulation of gene expression, organization of chromosome architecture, and signals controlling epigenetic inheritance.

The Human Genome Project produced the first complete sequences of individual human genomes. As of 2012, thousands of human genomes have been completely sequenced, and many more have been mapped at lower levels of resolution. The resulting data are used worldwide in biomedical science, anthropology, forensics and other branches of science. There is a widely-held expectation that genomic studies will lead to advances in the diagnosis and treatment of diseases, and to new insights in many fields of biology, including human evolution.

The haploid human genome contains approximately 20,000 protein-coding genes, significantly fewer than had been anticipated. Protein-coding sequences account for only a very small fraction of the genome (approximately 1.5%), and the rest is associated with non-coding RNA molecules, regulatory DNA sequences, introns, and sequences to which no function has yet been assigned.