lecture_12_new_and_improved2

lecture_12_new_and_improved2 - Lecture12CellDivision...

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Lecture 12 Cell Division Chromosome replication and partitioning Reading: Chapters 2, 3, 10.1
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General problems of replication and division. 1. One cell goes to two: Must duplicate all cellular material proteins, ribosomes, lipids, LPS, etc. 2. DNA replication and partitioning: Must duplicate and separate two 4.5 Mb molecules, maybe more?
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Some History? 1869 Identified 1910 Chemical composition determined 1920s Found in chromosomes along with protein 1944 Demonstrated as genetic material by Avery MacLeod and McCarry experiment 1953 Publication of DNA structure by Watson and Crick; structure confirmed by 1952 X ray diffraction photograph by Rosalind Franklin working in Wilkins’ Lab 1963 Nobel Prize awarded to Watson, Crick and Wilkins 1957 Rosalind Franklin passes at the age of 37 due to cancer, and no Nobel Prize
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Factoids Right handed helix, negatively super coiled: Look down on the helix it curves to the right Takes approximately 40 min/ 4.5 Mb genome 112.5kb/min 1.87 kb/sec @37 C Period of active replication: C period Period of cytokinesis (cytoplasim segragerion), i.e cell division: D period 20 min Total minimum time to make two E. coli cells from 1, is 60 min.
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Problem!!! E. coli growing at 37° C in rich medium or minimal complete + glucose grows with a generation time of approximately 20 min. How?
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Answer Multiple replication starts when cells are growing rapidly. In E. coli, cells monitor their Mass to DNA ratio At a specific Mass: DNA ratio, cells initiate a new round of replication.
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Example Cells growing with a 30 min generation 0 Division time line Initiation of replication time line 30 -30 -30 1.5 genome equivalents (ge) 2 X 50% of the genome 1 X 50% of the geneme
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This note was uploaded on 12/02/2009 for the course MIC 140 taught by Professor Meeks,singer during the Spring '09 term at UC Davis.

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lecture_12_new_and_improved2 - Lecture12CellDivision...

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