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polymerase chain reaction

(Encyclopedia)polymerase chain reaction pŏlˈĭmərāsˌ [key] (PCR), laboratory process in which a particular DNA segment from a mixture of DNA chains is rapidly replicated, producing a large, readily analyzed sa...

recombination

(Encyclopedia)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 ...

Wheeldon, Christopher

(Encyclopedia)Wheeldon, Christopher, 1973–, British ballet dancer and choreographer, studied Royal Ballet School, London. An outstanding contemporary classicist, Wheeldon creates dances that are lyrical, witty, s...

obesity

(Encyclopedia)obesity, condition resulting from excessive storage of fat in the body. Obesity is now usually defined using a formula known as the body mass index (BMI), in which weight (in kilograms) is divided by ...

osteoporosis

(Encyclopedia)osteoporosis ŏsˌtēōˌpərōˈsĭs [key], disorder in which the normal replenishment of old bone tissue is severely disrupted, resulting in weakened bones and increased risk of fracture; osteopenia...

Goodman, Benny

(Encyclopedia)Goodman, Benny (Benjamin David Goodman), 1909–86, American clarinetist, composer, and band leader, b. Chicago. Goodman studied clarinet at Hull House. In Chicago he had the opportunity to hear (and ...

episome

(Encyclopedia)episome ĕpˈĭsōm [key], 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 c...

species

(Encyclopedia)species, in biology, a category of classification, the original and still the basic unit in the demarcation of plant and animal types. The species marks the boundary between populations of organisms r...

race

(Encyclopedia)race, one of the group of populations regarded as constituting humanity. The differences that have historically determined the classification into races are predominantly physical aspects of appearanc...

differentiation

(Encyclopedia)differentiation, in biology, series of changes that occur in cells and tissues during development, resulting in their specialization. This, in turn, permits a greater variety of organisms. In plants, ...