Chapter 17

Chapter 17 - Chapter 17: the cell cycle A cell reproduces...

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Chapter 17: the cell cycle A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in 2 known as the cell cycle. The cell must produce 2 genetically identical daughter cells, the DNA in each chromosome must first be replicated to produce 2 complete copies, and the replicated chromosomes must then be accurately segregated to the 2 daughetr cells, so that each receives a copy of the entire genome The cell-cycle control system governs progression through the cell cycle. The fore of this system is an ordered series of biochemcail switches that initate the main events of the cycle. Inside the cell, the CCS monitors progession through the cell cycle and delays later events until earlier events have been completed. The EUK cell cycle is divided into 4 phases - S-phase: chromosome duplication - M- phase: chromosome segregation and cell division o Nuclear division o Cytokinesis - At the end of S-phase, the dna molecules in each pair of duplicated chromosomes are intertwined and held tightly together by specializsed protein linkages. - Prophase , 2 dna molecules are gradually disentangled and condensed into pairs of ridid rods called sister chromatids o Sister chromatids become attached to the mitotic spindle, and aligh at the spindle equator during metaphase - Anaphase: the destruction of sister chromatid cohesion sepearates the 2 chromatids - Telophase: chromosomes are packaged into separate nuclei - Cytokinesis: cleaves the cell in 2 - Gap phases: a lot more time for the cell to grow and double their mass of protein/organelles 4 duplication o G1: b/w M and S phase o G2: between S and M phase o the 2 phases are more than simple time delays to allow cell growth provide time for the cell to monitor the interal and external environment to ensure that conditions are suitable before the cell commits itself to S and mitosis
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Chapter 17 - Chapter 17: the cell cycle A cell reproduces...

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