Definitions

gene

gene

[jeen]
gene, the structural unit of inheritance in living organisms. A gene is, in essence, a segment of DNA that has a particular purpose, i.e., that codes for (contains the chemical information necessary for the creation of) a specific enzyme or other protein. The strands of DNA on which the genes occur are organized into chromosomes. The nucleus of each eukaryotic (nucleated) cell has a complete set of chromosomes and therefore a complete set of genes. Each gene provides a blueprint for the synthesis (via RNA) of enzymes and other proteins and specifies when these substances are to be made (see nucleic acid). Genes govern both the structure and metabolic functions of the cells, and thus of the entire organism and, when located in reproductive cells, they pass their information to the next generation.

Chemically, 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.

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. Open championship. He won it again in 1932, when he also won the British Open. He won the Professional Golfers Association championship three times (1922, 1923, 1933). His 1935 Masters win was punctuated by a 15th-hole final-round double eagle often called the most famous shot in golf history. One of the great golfers of all time, Sarazen won Seniors championships in the 1950s and played into his nineties.
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), where he starred in football and track. Drafted (1967) by the Oakland Raiders, he played left guard (1967-81) in 217 regular-season games, and his power, aggressiveness, and speed on the offensive line helped propel his team to Super Bowl victories in 1968, 1977, and 1981. After his retirement as a player, Upshaw became the first African-American executive director of the National Football League Players Association, serving from 1983 until his death. Tough and plain-spoken, he led the union in the contentious 1987 strike and through lengthy contract negotiations that led to free agency, high salaries, revenue sharing, and other significant player benefits. Upshaw was inducted into the Pro Football Hall of Fame in 1987.
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 in Paris won (1919) the light-heavyweight championship of the American Expeditionary Forces. In 1922 he defeated Battling Levinsky for the American light-heavyweight title, but lost it the same year to Harry Greb—the only fighter to defeat Tunney in the professional ring. Tunney regained the title in 1923. The well-proportioned, handsome, and intellectually inclined Tunney generally fought standing straight up and was known as a powerful counterpuncher. In 1926, he defeated Jack Dempsey in a 10-round decision in Philadelphia and became the world heavyweight champion. In Chicago a year later, Tunney repeated this performance in a return bout with Dempsey; the decision was the subject of much controversy because of the famous "long count" after Tunney was knocked down in the seventh round and Dempsey at first failed to move to a neutral corner. Tunney retired from the ring as heavyweight champion in 1928. In World War II he served (1940-45) in the U.S. navy, directing the program to keep naval personnel physically fit. After the war he successfully engaged in business. He wrote A Man Must Fight (1932) and Arms for Living (1942).

See biography by J. Cavanaugh (2006).

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 radio in Tulsa, Okla., during the 1920s. He later wrote or cowrote more than 250 songs, among them Back in the Saddle Again (1939) and Rudolph the Red-Nosed Reindeer (1948), and made some 600 recordings. He moved to Hollywood in the early 1930s and starred in his first film, Tumbling Tumbleweeds, (of nearly 100) in 1935. Autry, America's top Western star during 1937-43, usually played a singing, guitar-playing hero and rode his famous horse, Champion. After serving in World War II (1942-45), he resumed his film career and starred (1950-56) in a popular television program. Autry invested the fortune he amassed with skill, becoming the owner of many properties, including the California Angels baseball team. His collection of Western art and memorabilia is housed in the Autry National Center, Los Angeles.

See his autobiography (1978); biography by H. George-Warren (2007); D. Rothel, The Gene Autry Book (1988).

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 flying 89 missions and sorties in World War II, Roddenberry worked as a pilot and police officer. He joined the television industry as a scriptwriter, eventually becoming head writer for the series Have Gun, Will Travel. In 1966 he created Star Trek, which became a cultural icon. The show spawned several feature films and further television series.
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 Broadway musical Pal Joey (1940). He moved to Hollywood in 1941 and soon starred in his first film, For Me and My Gal (1942). His best-known work was in motion pictures, where he excelled in an inventive combination of camera and dance techniques in such films as On the Town (1949), An American in Paris (1951; Academy Award), Singin' in the Rain (1952)—which contains his single most famous performance—and Invitation to the Dance (1956). Athletically graceful, a skillful and expressive dancer with a joyfully muscular yet lyrical style, he also sang in a thin yet appealing voice. Kelly appeared in such film musicals as Anchors Aweigh (1945), Take Me Out to the Ballgame (1949), Brigadoon (1954), and Les Girls (1957). He also played dramatic film roles, as in Inherit the Wind (1960), and directed several movies, including The Happy Road (1950) and Hello Dolly (1969).

See biographies by C. Hirschhorn (1975) and A. Yudkoff (1999).

Introduction of genetic material (by interbreeding) from one population of a species to another, thereby changing the composition of the gene pool of the receiving population. The introduction of new characteristics through gene flow increases variability within the population and makes possible new combinations of traits. In humans, gene flow usually comes about through human migration.

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Unit of heredity that occupies a fixed position on a chromosome. Genes achieve their effects by directing protein synthesis. They are composed of DNA, except in some viruses that contain RNA instead. The sequence of nitrogenous bases along a strand of DNA determines the genetic code. When the product of a particular gene is needed, the portion of the DNA molecule that contains that gene splits, and a complementary strand of RNA, called messenger RNA (mRNA), forms and then passes to ribosomes, where proteins are synthesized. A second type of RNA, transfer RNA (tRNA), matches up the mRNA with specific amino acids, which combine in series to form polypeptide chains, the building blocks of proteins. Experiments have shown that many of the genes within a cell are inactive much or even all of the time, but they can be switched on and off. Mutations occur when the number or order of bases in a gene is disrupted. Seealso genetic engineering, genetics, Hardy-Weinberg law, Human Genome Project, linkage group.

Learn more about gene with a free trial on Britannica.com.

Gene that determines whether or not a trait determined by another gene will be expressed. For example, when the gene responsible for albinism occurs, the genes that determine skin color are present but not expressed; the gene for albinism is therefore called an epistatic gene.

Learn more about epistatic gene with a free trial on Britannica.com.

orig. James Joseph Tunney

(born May 25, 1898, New York, N.Y., U.S.—died Nov. 7, 1978, Greenwich, Conn.) U.S. boxer. Tunney boxed in the Marine Corps, earning the nickname “the Fighting Marine.” He defeated Jack Dempsey in 1926 to become the world heavyweight champion. In a controversial rematch in Chicago in 1927, Dempsey knocked Tunney to the canvas in the seventh round but failed to retire immediately to a neutral corner, thus delaying the count; the “long count” allowed Tunney to rise and win the 10-round fight. He retired the next year with a record of 65 wins in 77 bouts.

Learn more about Tunney, Gene with a free trial on Britannica.com.

orig. Eugene Saraceni

(born Feb. 27, 1902, Harrison, N.Y., U.S.—died May 13, 1999, Naples, Fla.) U.S. golfer, prominent in the 1920s and '30s. Born to a poor Italian immigrant family, Sarazen began caddying when he was eight. He became a professional golfer in 1920. Sarazen was the first to win the four tournaments that comprise golf's grand slam in modern times. Sarazen won the U.S. Open (1922, 1932), the British Open (1932), and the PGA Championship (1922–23, 1933) and completed the grand slam with his Masters victory in 1935. That Masters victory was highlighted by his famous double eagle, two strokes (three under par) on the par-five 15th hole.

Learn more about Sarazen, Gene with a free trial on Britannica.com.

in full Eugene Wesley Roddenberry

(born Aug. 19, 1921, El Paso, Texas, U.S.—died Oct. 24, 1991, Santa Monica, Calif.) U.S. television and film producer. He worked as a pilot (1945–49) and police officer (1949–53) before becoming a writer for television series such as Dragnet and Dr. Kildare. He created the idea for the Star Trek series and produced the show from 1966 until it ended in 1969; later rerun in syndication, it developed a durable cult following among fans known as “Trekkies.” He produced six Star Trek movies, and from 1987 to 1991 he produced the television series Star Trek: The Next Generation.

Learn more about Roddenberry, Gene with a free trial on Britannica.com.

orig. Eugene Curran Kelly

(born Aug. 23, 1912, Pittsburgh, Pa., U.S.—died Feb. 2, 1996, Beverly Hills, Calif.) U.S. dancer, choreographer, actor, and movie director. After training at his mother's dance school in Pittsburgh, he moved to New York in 1938 and danced in Broadway musicals, creating the h1 role in Pal Joey in 1940. Beginning in 1942, his athletic style and carefree acting—exemplified in the popular Anchors Aweigh (1945), On the Town (1949), An American in Paris (1951), and Singin' in the Rain (1952), which he also helped choreograph and direct—became hallmarks of the movie musical. His achievements earned him a special Academy Award in 1951. He later choreographed and directed numerous other movies and created a ballet for the Paris Opéra (1960).

Learn more about Kelly, Gene with a free trial on Britannica.com.

orig. James Joseph Tunney

(born May 25, 1898, New York, N.Y., U.S.—died Nov. 7, 1978, Greenwich, Conn.) U.S. boxer. Tunney boxed in the Marine Corps, earning the nickname “the Fighting Marine.” He defeated Jack Dempsey in 1926 to become the world heavyweight champion. In a controversial rematch in Chicago in 1927, Dempsey knocked Tunney to the canvas in the seventh round but failed to retire immediately to a neutral corner, thus delaying the count; the “long count” allowed Tunney to rise and win the 10-round fight. He retired the next year with a record of 65 wins in 77 bouts.

Learn more about Tunney, Gene with a free trial on Britannica.com.

orig. Eugene Saraceni

(born Feb. 27, 1902, Harrison, N.Y., U.S.—died May 13, 1999, Naples, Fla.) U.S. golfer, prominent in the 1920s and '30s. Born to a poor Italian immigrant family, Sarazen began caddying when he was eight. He became a professional golfer in 1920. Sarazen was the first to win the four tournaments that comprise golf's grand slam in modern times. Sarazen won the U.S. Open (1922, 1932), the British Open (1932), and the PGA Championship (1922–23, 1933) and completed the grand slam with his Masters victory in 1935. That Masters victory was highlighted by his famous double eagle, two strokes (three under par) on the par-five 15th hole.

Learn more about Sarazen, Gene with a free trial on Britannica.com.

in full Eugene Wesley Roddenberry

(born Aug. 19, 1921, El Paso, Texas, U.S.—died Oct. 24, 1991, Santa Monica, Calif.) U.S. television and film producer. He worked as a pilot (1945–49) and police officer (1949–53) before becoming a writer for television series such as Dragnet and Dr. Kildare. He created the idea for the Star Trek series and produced the show from 1966 until it ended in 1969; later rerun in syndication, it developed a durable cult following among fans known as “Trekkies.” He produced six Star Trek movies, and from 1987 to 1991 he produced the television series Star Trek: The Next Generation.

Learn more about Roddenberry, Gene with a free trial on Britannica.com.

orig. Eugene Curran Kelly

(born Aug. 23, 1912, Pittsburgh, Pa., U.S.—died Feb. 2, 1996, Beverly Hills, Calif.) U.S. dancer, choreographer, actor, and movie director. After training at his mother's dance school in Pittsburgh, he moved to New York in 1938 and danced in Broadway musicals, creating the h1 role in Pal Joey in 1940. Beginning in 1942, his athletic style and carefree acting—exemplified in the popular Anchors Aweigh (1945), On the Town (1949), An American in Paris (1951), and Singin' in the Rain (1952), which he also helped choreograph and direct—became hallmarks of the movie musical. His achievements earned him a special Academy Award in 1951. He later choreographed and directed numerous other movies and created a ballet for the Paris Opéra (1960).

Learn more about Kelly, Gene with a free trial on Britannica.com.

ASPM is a human gene whose defective forms are associated with autosomal recessive primary microcephaly.

"ASPM" is an acronym for "Abnormal Spindle-like, Microcephaly-associated", which reflects its being an ortholog to the Drosophila melanogaster "abnormal spindle" (asp) gene. ASPM is located on chromosome 1, band q31 (1q31).

The mouse gene, Aspm, is expressed in the primary sites of prenatal cerebral cortical neurogenesis. The difference between Aspm and ASPM is a single, large insertion coding for so-called IQ domains.

Evolution

A new allele (version) of ASPM appeared sometime between 14,100 and 500 years ago with a mean estimate of 5,800 years ago. The new allele has a frequency of about 50 percent in populations of the Middle East and Europe, it is less frequent in East Asia, and has low frequencies among Sub-Saharan African populations.

The mean estimated age of the ASPM allele of 5,800 years ago, roughly correlates with the development of written language, spread of agriculture and development of cities. Currently, two alleles of this gene exist: the older (pre-5,800 years ago) and the newer (post-5,800 years ago). About 10% of humans have two copies of the new ASPM allele, while about 50% have two copies of the old allele. The other 40% of humans have one copy of each. Of those with an instance of the new allele, 50% of them are an identical copy suggesting a highly rapid spread from the original mutation. According to a hypothesis called a "selective sweep", the rapid spread of a mutation (such as the new ASPM) through the population indicates that the mutation is somehow advantageous to the individual. As of today, there is no evidence to support the notion that the new ASPM allele increases intelligence, and some researchers dispute whether the spread of the allele even demonstrates selection. They suggest that the current distribution of the alleles could be explained by a founder effect, following an out of Africa dispersal. However, statistical analysis has shown that the older forms of the gene are found more heavily in populations that speak tonal languages like Chinese.

Diversity

Instead of ASPM, the DAB1 gene, which also increases the density of neural matter, appears to have come under selection in the Chinese.

References

Notes

  1. An IQ domain is a segment of DNA that codes for the IQ motif.
  2. ::IQ protein motif: [FILV]Qxxx[RK]Gxxx[RK]xx[FILVWY]
  3. :The term "IQ" refers to the first two amino acids of the motif: isoleucine (commonly) and glutamine (invariably).
  4. following is one of a large number of similar news articles:
  5. :
  6. Kniffin, Cassandra L. et al.
  7. :

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