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Documents for "Genetics and Genetic Engineering":
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adaptation
in biology, has several meanings. It can mean the adjustment of living matter to environmental conditions and to other living things either in an organism's lifetime (physiological adaptation) or...
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albino
[Port.,=white], animal or plant lacking normal pigmentation. The absence of pigment is observed in the body covering (skin, hair, and feathers) and in the iris of the eye. The blood vessels of the...
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atavism
the appearance in an individual of a characteristic not apparent in the preceding generation. At one time it was believed that such a phenomenon was thought to be a reversion of "throwback" to a...
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breeding
in agriculture and animal husbandry , propagation of plants and animals by sexual reproduction ; usually based on selection of parents with desirable traits to produce improved progeny. In conventional breeding, progeny inherit genes for both desirable and undesirable traits from both...
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chromosome
structural carrier of hereditary characteristics, found in the nucleus of every cell and so named for its readiness to absorb dyes. The term chromosome is usually reserved for the structure when it is condensed and readily visible during cell division (see mitosis ). At other times the chromosome appears as a fibrous structure, called the chromonema, consisting of accumulations (called chromomeres) of chromatin, the dye-absorbing material. During nuclear...
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crossing over
process in genetics by which the two chromosomes of a homologous pair exchange equal segments with each other. Crossing over occurs in the first division of meiosis. At that stage each chromosome has replicated into two strands called sister chromatids. The two homologous chromosomes of a pair synapse, or come together. While the chromosomes are synapsed,...
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Darwinism
concept of evolution developed in the mid-19th cent. by Charles Robert Darwin. Darwin's meticulously documented observations led him to question the then current belief in special creation of each species. After years of studying and correlating the voluminous notes he had...
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DNA fingerprinting
or DNA profiling, any of several similar techniques for analyzing and comparing DNA from separate sources, used especially in law enforcement to identify suspects from hair, blood, semen, or other biological...
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episome
unit of genetic material composed of a series of genes that sometimes has an independent existence in a host cell and at other times is integrated into a chromosome of the cell, replicating itself along with the chromosome. Episomes have been studied in bacteria. One group of episomes are actually viruses that infect bacteria. As autonomous units they destroy host cells, and as segments integrated into a chromosome they multiply in cell division and are transferred to daughter cells. Episomes called...
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eugenics
study of human genetics and of methods to improve the inherited characteristics, physical and mental, of the human race. Efforts to improve the human race through bettering housing facilities and other environmental...
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Eve
in genetics, popular term for a theoretical female ancestor of all living people, also known as mitochondrial Eve. In 1987 biochemist Allan C. Wilson proposed that all living human beings had...
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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...
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gene pool
the total of all genes in a population of a particular species. See genetics.
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genetic engineering
the use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. The techniques include the use of hybridomas (hybrids of...
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genetic screening
testing for genetic disorders. Most commonly, prospective parents or a fetus is tested when a specific genetic disorder is suspected (e.g., Tay-Sachs or sickle cell disease ). In such a case, genetic screening begins with a complete medical history of both parents. If the parents decide to conceive or have already conceived, diagnostic tests, such as chorionic villus sampling and amniocentesis , can be performed on the fetus to detect various genetic disorders. In the case of a positive finding, the parents can elect to abort the fetus. Embryo biopsy , another diagnostic test, can be used on an embryo conceived by in vitro fertilization to determine if the embryo is free of certain genetic diseases before it is implanted in the uterus. As researchers identify more genetic markers for diseases and develop blood tests for them,...
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genetics
scientific study of the mechanism of heredity. While Gregor Mendel first presented his findings on the statistical laws governing the transmission of certain traits from generation to generation in...
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heredity
transmission from generation to generation through the process of reproduction in plants and animals of factors which cause the offspring to resemble their parents. That like begets like has been a maxim since ancient times. Although the fact of heredity has been generally...
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Human Genome Project
international scientific effort to map all of the genes on the 23 pairs of human chromosomes and, to sequence the 3.1 billion DNA base pairs that make up the chromosomes (see nucleic acid ). Begun in 1990 with the goal of enabling scientists to understand the basis of genetic diseases and to gain insight into human evolution, the project was largely completed in 2000 when 85% of the...
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hybrid
term applied by plant and animal breeders to the offspring of a cross between two different subspecies or species, and by geneticists to the offspring of parents differing in any genetic...
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inbreeding
mating of closely related organisms. Inbreeding is chiefly used as a means of insuring the preservation of specific desired traits among the offspring of purebred animals (see breeding ). Continued inbreeding through many generations reduces the chances for diversity of characteristics in the offspring and tends to reduce vigor and fertility. Only in laboratory conditions can the...
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lysogeny
see bacteriophage ; recombination.
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mutation
in biology, a sudden, random change in a gene , or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any change in the delicate balance of an organism having a high level of...
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nucleic acid
any of a group of organic substances found in the chromosomes of living cells and viruses that play a central role in the storage and replication of hereditary information and in the expression of...
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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 active or not (operator...
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pharming
the use of genetically altered livestock, such as cows, goats, pigs, and chickens, to produce medically useful products. In pharming, researchers first create hybrid genes using animal DNA and the...
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polymerase chain reaction
(PCR), laboratory process in which a particular DNA segment from a mixture of DNA chains is rapidly replicated, producing a large, readily analyzed sample of a piece of DNA; the process is...
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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 of either parent, being rather a combination of genes from both parents. In recombination by crossing over , alleles of genes are exchanged between homologous chromosomes during meiosis. This exchange results in the generation of new combinations of alleles on segments of chromosomes, counteracting the tendency of linked genes, i.e., genes on the same chromosome, to be always...
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selection
In Darwinism , the mechanism of natural selection is considered of major importance in the process of evolution. Popular formulations sometimes envisage a struggle for existence in which direct competition for mates or for various factors in the environment (e.g., food, water, and suitable space) counteracts...
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sex
term used to refer both to the two groups distinguished as males and females, and to the anatomical and physiological characteristics associated with maleness and femaleness. Sex relates to the...
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sport
in biology: see mutation.
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