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A detailed overview of the cell cycle, mitosis, and meiosis. It covers the key phases of the cell cycle, the role of spindle microtubules and kinetochores during mitosis, the metaphase to anaphase transition, and the formation of haploid gametes during meiosis. The document also discusses the molecular organization of eukaryotic chromosomes, including the structure of nucleosomes and the concept of eu- and heterochromatin. It explores how chromatin state can impact gene expression, using the example of position-effect variegation in drosophila. Overall, this document provides a comprehensive understanding of the fundamental processes of cell division and chromosome inheritance.
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Blue: DNA Green: Microtubules, detected by immunofluorescence (antibody detection) IMPORTANT POINTS: -mitosis produces two identical daughter cells -the cell cycle underlies the mechanisms and checkpoints that constitute mitosis -meiosis consists in a reduction of ploidy and produces haploid gametes -meiosis is the basis for chromosomal inheritance
The Phases of the Cell Cycle: In actively dividing human cells: 24 hr Yeast cells: 1.5 hr Figure 3.
A word on terminology for chromosomes in diploid cells… Our somatic cells are diploid: there are two copies of each chromosome: one paternal, one maternal chromosome Our gametes are haploid: one chromosome for each (maternal or paternal)
Prophase: chromosome condensation-centrosome duplication-nuclear envelope breakdown Figure 3.
Figure 3. Kinetochores from two sister chromatids must be engaged from opposite poles for a productive interaction: until this happens for ALL chromosomes, anaphase does not occur
Cohesin holds sister chromatids together Separase cleaves cohesin and triggers anaphase Figure 3.
Mitosis produces to diploid cells with unduplicated chromosomes Figure 3.
Figure 3.
Figure 3. The homologs segregate independently in Anaphase I: This results in a reduction in ploidy: from diploid to haploid Each chromosome is duplicated: is composed of two sister chromatids The paternal and maternal chromosomes segregate independently
Figure 3. The sister chromatid segregate at this point: They may not be identical, because of recombination!
