DNA replication - 16 - 16-1Cell and Molecular Biology...

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Unformatted text preview: 16-1Cell and Molecular Biology (Biol. Chem. 410A)Lecture #16Harry R. Matthews, Ph.D.October 17, 1996DNA ReplicationClinical correlations:cancerLearning objectives:replicationcell proliferationcell cycleflow cytometryaneuploidytopoisomerasestelomeraseOptional reading:Stryer IV: Chapter 4.Alberts et al.: 3rd Ed., Chapter 3, pages 98-104; Chapter 6, 251-262, Chapter 17.omplete organisms are generated from a single cell that grows and then splits into two daughter cells. The process of growth and cell division continues and gen-erates the large numberabout 1013of cells found in the adult human. During cell growth, the DNA in the chromosomes replicates so that each daughter cell has identical chromo-somes. Although some genetic changes may occur through accident or programmed gene rearrangements, in general, the amount and information content of DNA is the same in all the cells of the body. Different cells carry out different functions by expressing a specific subset of the total genome. The unexpressed genes are present but not used. Some inform-ation is passed from cell to daughter cell by means other than DNA sequence, such as the pattern of DNA methylation, specific chromat-in structures or centriole structure. These are epigenetic mechanisms. The combined pro-cesses of cell growth and cell division are called cell proliferation.CCell proliferation is under sophisticated control in the body, by internal controls, direct cell-cell contacts and indirect cell-cell interac-tions through hormones. Random somatic mutations due to chance or environmental mutagens, combined with inherited defects, can affect the genes in any cell. Usually such damage results in a cell that is not viable or can be recognized and destroyed by the im-mune system. Sometimes, however, a combin-ation of subtle changes occurs that leads to loss of regulation of cell proliferation without triggering the immune system. In this case, a cell will begin to proliferate, will pass on the defective genes to its daughters which will continue to proliferate and so on to produce a tumor. Some of these tumors will develop the ability to invade other tissues and this is called cancer. This chapter covers the basic processes of DNA replication and related topics in cell pro-liferation. Regulation of cell proliferation was touched on in the discussion of the MAP kinase cascade in the lecture on covalent modifications of proteins and these ideas will be developed further in the group of lectures beginning with Oncogenes....
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DNA replication - 16 - 16-1Cell and Molecular Biology...

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