Meiosis, Variation, and Mendel's Principles

Notes

🧬 Meiosis & Genetics Study Sheet 1. The Two Main Goals of Meiosis Meiosis is different from Mitosis. While Mitosis makes clones, Meiosis has two specific jobs: 1. Reduce Ploidy: Cuts the chromosome number in half (2n→n) so fertilization restores the correct number. 2. Generate Variation: Ensures offspring are genetically unique from parents and siblings. 2. How Meiosis Creates Variation There are two "shuffling" mechanisms that make you unique. A. Crossing Over (Recombination) ● When: Prophase I (Early Meiosis I). ● The Action: Homologous chromosomes "synapse" (stick together). Non-sister chromatids physically break and swap DNA sections. ● The Result: Recombinant Chromosomes. A single chromosome now contains a mix of maternal (mom) and paternal (dad) alleles. ● The Hand Model: ○ Left hand = Paternal homolog; Right hand = Maternal homolog. ○ Index/Middle fingers = Sister chromatids. ○ Touching index fingers together = Synapse of non-sister chromatids. B. Independent Assortment ● When: Metaphase I. ● The Action: Homologous pairs line up at the center of the cell. They line up randomly. The "Mom" version of chromosome 1 doesn't care which side the "Mom" version of chromosome 2 picks...