Word: nucleus
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...began to suspect the cause. He had just returned from a medical seminar on a newly recognized disorder called Fragile X syndrome, which results from a weakness in the structure of the X sex chromosome (one of the 46 chromosomes -- complex molecules containing long segments of DNA -- in the nucleus of the human cell). The behavior of the Lancaster children seemed to fit the patterns described at the meeting, and tests at Denver's Children's Hospital soon confirmed that they both had the defective chromosome...
Most of the DNA in human cells is in the cell nucleus, in the form of chromosomes. Since chromosomes come from both parents, this nuclear DNA is reshuffled with each generation, confusing the line of inheritance. But there is also DNA outside the nucleus, in mitochondria, substructures within each cell that are responsible for producing energy the cell needs. Since the sperm's mitochondria do not survive fertilization intact, mtDNA is inherited solely through the mother. The only way it can change over the generations is through mutation. And that mutation, evidence suggests, proceeds at a steady, known rate...
...origin of galaxies and other puzzling celestial phenomena. It combines some of the most advanced ideas in astrophysics and elementary-particle physics, and joins the independent research of Ostriker and Physicist Edward Witten. The unifying element: the cosmic strings -- bizarre, hypothetical entities that are thinner than an atomic nucleus, as long as the universe is wide, and so dense that a mile-long segment would weigh as much as the earth...
Harvard Coach Bill Cleary '56 says Yale still "has a good nucleus...
...remarkable transformation takes place. With the help of the enzyme, the naked AIDS virus converts its RNA into double-stranded deoxyribonucleic acid (DNA), the master molecule of life. The molecule then penetrates the cell nucleus, inserts itself into a chromosome and takes over part of the cellular machinery, directing it to produce more AIDS viruses. Eventually, overcome by its alien product, the cell swells and dies, releasing a flood of new viruses to attack other cells, including more helper T cells and macrophages. The immune system, deprived of a crucial number of those vital T cells, is unable to direct...