More Sponsored Links For:
geneChemically, each gene consists of a specific sequence of DNA building blocks called nucleotides. Each nucleotide is composed of three subunits: a nitrogen-containing compound, a sugar, and phosphoric acid. Genes may vary in their precise makeup from person to person, including, for example, one nucleotide in a certain location in some people but another nucleotide in that location in others. Geometrically, the gene is a double helix formed by the nucleotides. Gene loci are often interspersed with segments of DNA that do not code for proteins; these segments are termed junk DNA. When junk DNA occurs within a gene, the coding portions are called exons and the noncoding (junk) portions are called introns. Junk DNA makes up 97% of the DNA in the human genome, and, despite its name, is necessary for the proper functioning of the genes.
Each chromosome of each species has a definite number and arrangement of genes. Alteration of the number or arrangement of the genes can result in mutation. When the mutation occurs in the germ cells (egg or sperm), the change can be transmitted to the next generation. Mutations that affect somatic cells can result in certain cancers.
The scientific study of inheritance is genetics. The genetic makeup of an organism with reference to its set of genetic traits is called its genotype. The interaction of the environment and the genotype produces the observable attributes of the organism, or its phenotype. The sum total of the genes contained in an organism's full set of chromosomes is termed the genome. Scientists are working toward identifying the location and function of each gene in the human genome (see Human Genome Project). The decoding of the first free-living organism (a bacterium, Hemophilus influenzae) was completed in 1995 by J. Craig Venter and Hamilton Smith.
See also gene therapy; genetic engineering.
The Columbia Encyclopedia. Copyright © 2001-09 Columbia University Press. All rights reserved.
- gene pool
Gene pool, the total of all genes in a population of a particular species. See genetics.
- gene therapy
Gene therapy, the use of genes and the techniques of genetic engineering in the treatment of a genetic disorder or chronic disease. There are many techniques of gene therapy, all of them still...
- Autry, Gene
Autry, Gene (Orvon Grover Autry), 1907–98, American entertainer and businessman, b. Tioga Springs, Tex. Probably the most successful of the movies' singing cowboys, Autry began singing on the ...
- Roddenberry, Gene
Roddenberry, Gene (Eugene Wesley Roddenberry), 1921–91, American television writer and producer, b. El Paso, Tex. After being awarded the Distinguished Flying Cross and the Air Medal for flyin...
- Kelly, Gene
Kelly, Gene, 1912–96, American dancer, choreographer, movie actor, and director, b. Pittsburgh. Kelly started dancing on Broadway in 1938 and first gained fame in the title role of the Broadwa...
- Upshaw, Gene
Upshaw, Gene (Eugene Upshaw, Jr.), 1945–2008, American football player and labor union leader, b. Robstown, Tex. He attended Texas College of Arts and Industries (now Texas A&M, Kingsville), w...
- Sarazen, Gene
Sarazen, Gene, 1902–99, American golfer, b. Harrison, N.Y. The son of an Italian immigrant carpenter, he entered golf as a caddie at Rye, N.Y. In 1922—at the age of 20—Sarazen won the U.S. Ope...
- Tunney, Gene
Tunney, Gene (James Joseph Tunney), 1898–1978, American boxer, b. New York City. He began boxing in neighborhood clubs as a youngster. In World War I, he served in the U.S. marines and while i...
- operon
Operon, in genetics, site on a bacterial chromosome containing genes that control protein synthesis (structural genes) together with a gene that determines whether the structural genes are act...
- recombination
Recombination, process of shuffling of genes by which new combinations can be generated. In recombination through sexual reproduction, the offspring's complete set of genes differs from that o...
