HUMAN DNA
The Map of Life
Deoxyribonucleic acid (DNA) is the chemical inside the nucleus of all cells that carries the genetic instructions for making living organisms.
A DNA molecule consists of two strands that wrap around each other to resemble a twisted ladder - a helix.
Four different bases are present in DNA –
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Proteins perform most life functions and make up the majority of cellular structures.
Repeated sequences that do not code for proteins ("junk DNA") make up 80-90% of the human genome. It is here that we have the most flexibility to enhance or design better structures. "Junk DNA" is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified. While much of this sequence may be an evolutionary artifact that serves no present-day purpose, some is believed to function in ways that are not currently understood.
Human DNA has approximately 3 billion chemical base pairs, and there are approximately 20,000-25,000 genes in human DNA
DNA in the human genome is arranged into 24 or 26 pairs of distinct chromosomes--physically separate molecules that range in length from about 50 million to 250 million base pairs.
A few types of major chromosomal abnormalities, including missing or extra copies or gross breaks and rejoinings (translocations), can be detected by microscopic examination. Most changes in DNA, however, are more subtle and require a closer analysis of the DNA molecule to find perhaps single-base differences.
In May 2006, Human Genome Project researchers announced the completion of the DNA sequence for the last of the 24 human chromosomes.
