Download Chapter 11.4: Meiosis How many chromosomes do humans have

Chapter 11.4: Meiosis
How many chromosomes do humans have?
Diploid:
Haploid: What are homologous chromosomes?
Meiosis: Remember: this is DIFFERENT from mitosis because mitosis results in 2 identical,
diploid cells.
Phases of Meiosis (PMAT)
Interphase: DNA replication & cell growth (same as in mitosis)
Chromosome count: Meiosis I: separation of homologous chromosomes
• Prophase I: homologous chromosomes form a tetrad (crossing over occurs);
nuclear membrane breaks down; centrioles separate
• Metaphase I: homologous chromosomes line up side-by-side in the middle of
the cell; spindles attach at centromere
• Anaphase I: homologous chromosomes separate to opposite sides of the cell
• Telophase I: nuclear membrane reforms & cell begins to separate into two.
Cytokinesis: Cell separates into two diploid cells
**No Interphase = No DNA Replication**
Chromosomes Count: Meiosis II: separation of sister chromatids (very similar to mitosis)
• Prophase II: nuclear membrane breaks down, centrioles separate
• Metaphase II: chromosomes move to the middle of the cell (not side-by-side);
spindles attach at centromere
• Anaphase II: sister chromatids pulled apart by spindles; move to opposite sides
of the cell
• Telophase II: each cell begins to cleave into two cells Cytokinesis: Cell separates into 4 genetically different, haploid cells