Mitosis - September 10

Mitosis - September 10 - September 10, 2009 Chapter 10...

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September 10, 2009 Chapter 10 – Chromosomes and the Cell Cycle I) General Background a. What is the significance of the chromosomes in term of information? i. Major carriers of genetic information 1. 19 th Century Mendel – genetic inheritance 2. 1880 Walter Fleming – discovered the importance of chromatin and cell division 3. 1903 Sutton and Boveri – carriers of genes II) Prokaryotic Cell Reproduction a. Contain circular DNA molecules i. E coli has 4x10^6 base pairs of DINA in one single circular DNA molecule ii. Spans 1000 times the length of the cell iii. Twisted and folded to fit b. Reproduction i. Starts in origin of replication on circular DNA ii. Replication then goes around the circular DNA both ways III) Eukaryotic Cell Reproduction a. During cell division, chromatin fibers condense and become visible to become Chromosomes b. DNA is wound around specific proteins to form chromatin, which in turn is folded and packaged to make individual chromosomes
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i. Human has about 46 chromosomes ii. Roundworm has 2 chromosomes iii. Most other animal species have 8-50 chromosomes per cell c. Have more DNA than bacteria i. Multiple chromosomes ii. DNA in eukaryotes is about 1000 times than in any bacteria 1. Sperm contains 3x1^9 base pairs (1 m long) but has to fit into a nucleus that is 10 um 2. DNA has to be packaged into nucleus by Nucleosomes d. Nucleosomes i. Histone (protein which is (+) from amino acids) beads wrapped in DNA (which is -) ii. 146 base pairs of DNA wrapped around a core of 8 histone molecules iii. 8 histone pairs is made by 4 duplicates iv. Think of Nucleosomes as cotton reel v. DNA connecting Nucleosomes is called linker DNA vi. Scaffolding Proteins 1. Structure of the nucleosome is maintained using non- histone proteins called scaffolding proteins 2. DNA fibers unravel when removed from these proteins 3. Therefore, histone and non-histone proteins play a role in gene expression regulation by maintaining integrity vii.Non-histone protein and histone proteins are interlinked in jobs
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e. Chromosome Organization i. Nucleosomes (10nm) pack together; histone H1 helps stabilize the linker DNA ii. Nucleosomes pack into 30 nm chromatin fiber iii. 30 nm chromatin fibers extend to form 300 nm fibers, which then form coiled loops held together by scaf. Protein iv. Then condense together to form chromosome v. IV)Eukaryotic Cell Cycle i. Not all cells divide ii. Can last from 8 to 20 hours iii. 12 Hour cycle of Cell would mean 1. Inter phase (11.5 h) 2. M phase (.5 h) iv. Two Stages 1. Inter-phase a. Cell is actively preparing for M phase by synthesizing proteins b. When not actively dividing, cells will remain in G1 in an arrested state called G0 i. This is usually because of terminally divided or cells become too specialized c. If preparing for division at the end of G1 cells make
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This note was uploaded on 07/17/2010 for the course 119:101 101 taught by Professor Martin during the Spring '10 term at Rutgers.

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Mitosis - September 10 - September 10, 2009 Chapter 10...

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