Chapter 9 - BSC 1010 Dr. Presley Chapter 9 CELL DIVISION...

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BSC 1010 Dr. Presley Chapter 9 CELL DIVISION REQUIREMENTS FOR CELL DIVISION: 1. Reproductive signal to induce division 2. Replication of the DNA and vital cell components 3. Distribution of replicated DNA 4. Cytokinesis to provide membrane separation BACTERIAL REPRODUCTION - review bacterial cell structure (prokaryote) Review Fig. 4.5 on page 66 - nucleoid– region containing bacterial chromosome, not membrane bound - single chromosome made up of a circular DNA molecule - prokaryotic DNA lacks the proteins associated with eukaryotic DNA - protective structures external to its cell membrane - reproductive signal - usually comes from the external environmental ex. Escherichia coli – divides every 40 min at 37 o C, - if abundant nutrients as well, can divide every 20 min. - replication of DNA - begins at one point called the “ori” (origin of replication) - the “ori” attaches to cell membrane - DNA polymerase – enzyme that reads DNA to produce identical DNA - replication finishes at the “ter” (terminus of replication) - segregation of DNA – since the ori of the two DNA molecules (produced by DNA replication) are attached to the cell membrane, as the bacterium grows, the DNA molecules are moved apart. - cytokinesis – begins about 20 min. after chromosome duplication - cell membrane pinches inward separating the cytoplasm into two - tubulin-like fibers are involved in this purse-string constriction - new cell wall laid down between cells - Summary of BINARY FISSION ** Study Figure 9.2 on page 166 * DNA replicates, each chromosome attached to the cell membrane * cell elongates and separates chromosomes * cell membrane pinches inward * two daughter cells are produced which are IDENTICAL to parent cell - asexual reproduction – produces two identical daughter cells identical to parent - plasmids (accessory rings of DNA) also replicated at time of cell reproduction, more about the importance of plasmid reproduction in biotechnology studies EUKARYOTE CELL DIVISIONS – overview - review eukaryotic cell structure Study Fig. 4.7, p. 68-69 - many chromosomes (Table 9.1, p. 177 shows # chr. pairs per species) - chromosomes protected by nuclear envelope of nucleus - control of cell division is based on need of entire organism - some cells become unable to divide after specialization (differentiation) - ex. nerve cells, muscles, and red blood cells - NUCLEAR DIVISIONS = karyokinesis (term means division of nucleus) - MITOSIS - produces 2 genetically identical daughter nuclei - cells produced with the same number of chromosomes as parent - functions: growth and repair in multicellular organisms reproduction in unicellular organisms - occurs in somatic cells of multicellular organisms * Study Figure 9.8 on page 172 -173 - MEIOSIS - produces 4 haploid daughter nuclei - cells produced have half the number of chromosomes as parent - functions in sexual reproduction - provides for variation (diversity) due to new gene combinations - occurs in reproductive organs of plants and animals
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Chapter 9 - BSC 1010 Dr. Presley Chapter 9 CELL DIVISION...

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