Genetic Primer英文电子书.pdf

Genomics and Its Impact on Medicine and Society A 2001 Primer U.S. Department of Energy Human Genome Program: /hgmis The Basics DNA in the human genome is arranged into 24 distinct chromosomes—physically Cells are the fundamental working units separate molecules that range in length from of every living system. All the instructions needed about 50 million to 250 million base pairs. A to direct their activities are contained within few types of major chromosomal abnormalities, the chemical DNA (deoxyribonucleic acid). including missing or extra copies or gross DNA from all organisms is made up of breaks and rejoinings (translocations), can be the same chemical and physical components. detected by microscopic examination. Most The DNA sequence is the particular side-by- changes in DNA, however, are more subtle and side arrangement of bases along the DNA require a closer analysis of the DNA molecule strand (e.g., ATTCCGGA). This order spells out to find perhaps single-base differences. the exact instructions required to create a Each chromosome contains many genes, particular organism with its own unique traits. the basic physical and functional units of The genome is an organism’s complete heredity. Genes are specific sequences of bases set of DNA. Genomes vary widely in size: the that encode instructions on how to make smallest known genome for a free-living organ- proteins. Genes comprise only about 2% of the ism (a bacterium) contains about 600,000 human genome; the remainder consists of DNA base pairs, while human and mouse