What is a chromosome?
Chromosomes are structures that are located within cells, inside an organelle called the nucleus, and they contain all of the genetic information necessary for cell growth, replication and function. Chromosomes are made of long strands of DNA (deoxyribonucleic acid, also called the genetic material) that are wrapped around small circular proteins called histones. Each cell contains almost two yards of DNA. All cells contain the same DNA, but not all cells make the same types of proteins. The types of proteins that a cell will make, and therefore the functions of the cell, are determined by the way in which the strands of DNA are wrapped around the histones. DNA is wrapped around the histones in such a fashion that only the regions of DNA that are exposed can be used to make proteins. Chromosomes can be seen, with the aid of a microscope, only when a cell is preparing to divide in two or replicate itself (a process called mitosis). Most cells contain 23 pairs of chromosomes (46 in total) that line up in the center of the cell at the beginning of mitosis. During mitosis the chromosome pairs separate, the cell begins to pinch inward in the center to form two separate cells, and each cell receives one copy of each chromosome. After this occurs, both of the new cells have 23 chromosomes and a copy of each single chromosome is made so that the normal number of 46 chromosomes is restored. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Journal of Pathology
New-variant Creutzfeldt-Jakob disease
The most common transmissible spongiform encephalopathy (TSE) to occur in humans is called Creutzfeldt-Jakob disease (CJD). The TSE agent is capable of forming multiple strains, not unlike a virus, which has caused four different forms of CJD to be identified. The clinical features one of the strains, the so-called new variant CJD, and ways of diagnosing it are detailed.
Publication Name: World Health
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