01-Mitosis_Meiosis

01-Mitosis_Meiosis - Mitosis:Chapter10 CellDivision...

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Cell Division Office Hours: MF 3107  BROWN 11:30-12:30 M (Brown 3107) 10:00-11:00 Thursday (Lily B406E) No appointment necessary PSO:  Wednesday 11:30 Lilly 1-105 1:30 Lilly G-126 2:30 Lilly G-126 Cell division  - Melanoma, a type of skin cancer cause by uncontrolled growth of melanocytes Reproduction is a key element of life Requires 3 things: 1. Replication of genetic material 2. Accurate segregation of genetic material 3. Division of cytoplasm Process needs to be controlled Responsive to environmental conditions Bacteria divide by binary fission Prokaryotes have simple form of cell division DNA duplication and segregation a concerted process, are coupled Lot less genetic material than eukaryotes o Usually singular, circular chromosome 1 Mitosis: Chapter 10 Meiosis: Chapter 11
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Replication begins at unique site o Origin of replication o Bidirectional to unique site: terminus Prokaryotic Chromosome compaction Chromosome larger than cell Chromosome must be compacted, folded o Complex with proteins o Supercoiled by topoisomerase Problem for replication and segregation Chromosome is also attached to plasma membrane Binary fission Segregation once thought to be passive o Now known to be an active process o Replicated DNA actively partitioned to different ends of cell o Requires specific sequences near origin Growth of new membrane and a septum partitions of other cell contents 2
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o Septum forms at site of ring of FtsZ protein o FtsZ resembles microtubule protein tubulin involved in eukaryotic  mitosis Figures 10.1, 10.2 Eukaryotic chromosomes Homologue     : same chromosome, different parent Sister chromatid     : one of two exact copied of a replicated chromosome Centromere     : visible constriction (near center of chromsome, not always in  center) o Short repeated DNA sequences Kinetochore     : proteins attached to centromere o Connect chromosomes to microtubules during mitosis Cohesin     : complex of proteins holding sister chromatids together Figure 10.7 Problems cells must solve Chromosome compaction o Chromosomes are too long to fit into cell Means must always be folded o Even greater compaction for separation Replication and chromosome separation occur at different times 3
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o Chromosomes are not “labeled” o Means must keep chromatids of chromosomes attached until  separation o Release of attachment is irreversible Cleavage of cohesin Eukaryotic Chromosome compaction Chromosomes are very long and must be condensed to fit within the nucleus o DNA is complexed with histone proteins
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01-Mitosis_Meiosis - Mitosis:Chapter10 CellDivision...

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