Chapter 8

Chapter 8 - 1 Overview of Cell Division Mechanisms •...

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Unformatted text preview: 1. Overview of Cell Division Mechanisms • Challenge of dividing cell: daughter cell must get info encoded in parental DNA and enough cytoplasm to begin own operation- DNA “tells” which proteins to build; some are structural materials, some are enzymes that speed construction of organic compounds.- If cell does not inherit required info, will not grow/function properly- Parent cell’s cytoplasm already has enzymes, organelles, and other metabolic machinery. When daughter cell inherits “blob” of cytoplasm, it is really getting start-up machinery hat will keep it running until it can use info in DNA for growing on its own • Eukaryotic cells can’t split in two b/c single nucleus holds DNA- Split cytoplasm into daughter cells, but not until DNA is copied, sorted and packaged • Mitosis → nuclear division mechanism that occurs in somatic (body) cells- Basis of increases in body size during growth, replacement of worn out or dead cells, and tissue repair- Many plants, animals, fungi, and single-celled protists also reproduce asexually by mitosis • Meiosis → nuclear division mechanism that functions only in sexual reproduction- Precedes formation of gametes (i.e. sperm or eggs) or spores; in complex animals, gametes form germ cells • Prokaryotic cells reproduce asexually by prokaryotic fission • Every eukaryotic cell has characteristic # DNA molecules with attached proteins, which together form chromosomes • Chromosomes duplicated before cell enters nuclear division • Chromosome and copy attached as sister chromatids until late in nuclear division process • Early in mitosis/meiosis, chromosome coils back on itself repeatedly to a highly condensed form, by interactions b/w proteins and DNA • Nucleosome → histone-DNA spool; unit of structural organization • Centromere → pronounced constriction appearing in a predictable location along its length; site of attachment of sister chromatids- On the surface of the centromere are found kinetochores → docking sites for microtubules that will move the chromosome during nuclear division- Defining characteristic; varies among chromosomes 2. I ntroducing the Cell Cycle •...
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Chapter 8 - 1 Overview of Cell Division Mechanisms •...

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