Meiosis SC Standard B4.5- The student will be able to summarize the characteristics of the phases of Meiosis I and II

Meiosis Much like Mitosis, but two rounds. Sexual reproduction versus autosomal cell division End results= 4 haploid daughter cells versus 2 genetically identical daughter cells (diploid)

Meiosis I and Meiosis II: Meiosis I: Chromosome pairs replicate resulting in 2 haploid daughter cells with duplicated chromosomes different from original diploid cell Meiosis II: haploid daughter cells from Meiosis I divide resulting in 4 haploid daughter cells called gametes with undoubled chromosomes

Meiosis I: Interphase- cells grows, synthesize proteins and first round of DNA replication = duplicate chromosomes, cell prepares for division Prophase I- Nuclear membrane breaks down, spindle fibers appear, centrioles move to opposite poles. Each chromosome pairs with it’s corresponding homologous chromosome to form a tetrad Two sister chromatids are attached at centromere. Crossing over occurs here if it occurs

Meiosis I Continued Metaphase I- spindle fibers attach at the centromere and are pulled into the middle of the cell Anaphase I- spindle fibers pull homologous chromosomes towards opposite poles. Telophase I and Cytokinesis- nuclear membrane forms, cytoplasm divides, cells separate into 2 haploid daughter cells- each with half the number of chromosomes

Meiosis I prophase I metaphase I anaphase I telophase I

Meiosis II Prophase II- spindle fibers form, nuclear membrane breaks down Metaphase II- spindle fibers attach and chromosomes line up across the center of the cell Anaphase II- sister chromatids separate and move to opposite poles Telophase II and cytokinesis- nuclear membrane reforms, results in 4 haploid daughter cells (N)

Meiosis II

Comparing: Mitosis Meiosis: 2diploid daughter 4 haploid daughter cells (2N) cells (N) Body cells reproductive cells Production reduction process process Both have similar phases they go through