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Meiosis Overview

MEIOSIS OVERVIEW

  • Meiosis is the process of forming gametic cells, crucial for sexual reproduction.

CELL CYCLE STAGES

  • G1: Normal cell functions.

  • S: DNA replication.

  • G2: Preparation for division (protein synthesis).

  • M: Nuclear division (includes Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis).

VOCABULARY

  • Diploid: Cells with 2 sets of chromosomes (body cells).

  • Haploid: Cells with 1 set of chromosomes (sex cells).

  • Somatic cells: Normal diploid body cells.

  • Gametic cells: Haploid sex cells (egg and sperm).

  • Meiosis: Produces four genetically unique haploid cells, increasing genetic diversity.

  • Homologous Chromosomes: Pairs with the same genes at the same loci.

  • Sister chromatids: Identical chromosome copies post-replication.

  • Autosomes: Chromosome pairs 1-22; Sex chromosomes: Pair 23 (XX or XY).

  • Zygote: First cell formed when sperm fertilizes the egg.

MEIOSIS STAGES

MEIOSIS I

  • Prophase I: DNA condenses, crossing over occurs, nuclear membrane breaks down, spindle fibers form.

  • Metaphase I: Homologous chromosomes align randomly at the metaphase plate; spindle fibers attach to centromeres.

  • Anaphase I: Homologous chromosomes separate to opposite poles.

  • Telophase I: Chromosomes reach poles, nuclear membrane reforms, followed by cytokinesis creating two daughter cells.

MEIOSIS II

  • Prophase II: Nuclear membrane breaks down, spindle fibers form.

  • Metaphase II: Chromosomes line up at metaphase plate; spindle fibers attach to centromeres.

  • Anaphase II: Sister chromatids separate and move to opposite poles.

  • Telophase II: Nuclear membrane reforms, chromosomes decondense; cytokinesis yields four haploid cells (males: 4 sperm; females: 1 egg + 3 polar bodies).

MITOSIS VS. MEIOSIS

Mitosis

  • Produces two genetically identical diploid cells.

  • Chromosome number remains unchanged.

Meiosis

  • Produces four genetically unique haploid cells.

  • Chromosome number reduced by half.

GENETIC LINKAGE

  • Genes on the same chromosome are inherited together; likelihood of crossing over increases with distance between genes.

  • Gene Mapping: Shows gene locations along chromosomes.