Word: dna
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Dates: during 1990-1999
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...goal is grand -- and maddeningly difficult to achieve. Ever since Watson and Crick first deciphered the structure of DNA in 1953, doctors have had visions of treating disease not from the outside, with drugs or scalpels, but from the inside, by altering the primal instructions tucked in the nucleus of living cells...
...these things alive? That depends on how the term is defined. Surprisingly, there is no clear definition of "life." Most of the criteria put forward in the past are anthropocentric. Life on earth is carbon-based and built around the nucleic acids RNA and DNA, but that may be a historical accident. Most living things metabolize and multiply, but not all. Viruses have no metabolisms of their own; mules cannot reproduce. Many living things grow, but so do clouds and garbage dumps...
...sperm must carry a Y chromosome to fertilize a mother's egg, which always bears an X chromosome. But the site of the specific gene on Y that determines maleness has been elusive. Last week, though, scientists in Britain announced in Nature that they have identified a section of DNA that apparently directs the development of the testes, the male reproductive glands. The gene is being called SRY for sex-determining region...
Scientists from London's Imperial Cancer Research Fund studied DNA from four men with an abnormal set of chromosomes: each bore an XX pairing that had a small piece of Y attached to one of the chromosomes. Segments of DNA cloned from the Y fragment were compared with genetic material from a wide range of male and female mammals, from chimps to tigers. Only one segment, which contained the SRY gene, was present in all the males and absent in all the females. Working with the ICRF team, London's Medical Research Council scientists showed that XY mice, which...
Epidermal cells become malignant when the DNA in their nuclei is altered, causing them to divide uncontrollably and form tumors. The transformation of DNA can be caused by repeated X-ray exposure, burns, infectious disease or frequent contact with certain chemicals. But by far the most common culprit is the sun's ultraviolet light. After years of exposure to sunlight, the damage becomes visible first as small, scaly, precancerous spots called keratoses, usually on middle-aged or older people and in areas of the skin generally not protected by clothing. These spots can turn malignant, becoming translucent basal-cell nodules...