BILD 1 Ch 12-18 Book Notes

BILD 1 Ch 12-18 Book Notes - Chapter 12 The Cell Cycle •...

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Unformatted text preview: Chapter 12: The Cell Cycle • The ability of organisms to reproduce their own kind is the one characteristic that best distinguishes living things from nonliving matter • The continuity of life is based on the reproduction of cells, or cell division • The cell division process is an integral part of the cell cycle , the life of a cell from the time it is first formed from a dividing parent cell until its own division into two cells 12.1 Cell division results in genetically identical daughter cells Cellular Organization of the Genetic Material • A cell’s endowment of DNA, its genetic information, is called its genome • Although a prokaryotic genome is often a single long DNA molecule, eukaryotic genomes usually consist of a number of DNA molecules o Overall length of DNA in a typical eukaryotic cell is about 2m • The replication and distribution of so much DNA is manageable because the DNA molecules are packaged into chromosomes , so named b/c they take up certain dyes used in microscopy • Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus • Somatic cells : all body cells except the reproductive cells – humans: contain 46 chromosomes, made up of 23 from each parent • Reproductive cells, or gametes – sperm cells and egg cells – have half as many chromosomes as somatic cells, or one set of 23 chromosomes in humans • Eukaryotic chromosomes are made of chromatin , a complex of DNA and associated protein molecules o Each single chromosome contains one very long, linear DNA molecule that carries several hundred to a few thousand genes, the unites that specify an organism’s inherited traits o The associated proteins maintain the structure of the chromosomes and help control the activity of the genes Distribution of Chromosomes During Cell Division • When a cell is not dividing, and even as it duplicates its DNA in preparation for cell division, each chromosome is in the form of a long, thin chromatin fiber o After DNA duplication, h/e, the chromosomes condense: Each chromatin fiber becomes densely coiled and folded, making the chromosomes much shorter and thicker – can see with microscope o • Each duplicated chromosome has two sister chromatids – the two chromatids, each containing an identical DNA molecule, are initially attached by adhesive proteins all along their lengths o In its condensed form, the duplicated chromosome has a narrow “waist” at a specialized region called the centromere , where the 2 chromatids are most closely attached • Once the sister chromatids separate during mitosis, they are considered individual chromosomes...
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This note was uploaded on 11/16/2008 for the course BILD BILD1 taught by Professor Bever during the Winter '08 term at UCSD.

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BILD 1 Ch 12-18 Book Notes - Chapter 12 The Cell Cycle •...

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