The document defines a gene as a unit of heredity and an allele as a variant form of a gene. It lists the 8 stages of meiosis as prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II and telophase II. It explains that homologous chromosomes are pairs of chromosomes that contain the same genes but not necessarily the same alleles, and that crossing over occurs during prophase I and involves the exchange of genetic material between homologous chromosomes, leading to increased genetic variation.

1. Launch Write the definition of a gene and an allele. What are the 8 stages of meiosis?

2. Cell Division In cell division, new cells are made from an old cell. During cell division, these chromosomes are copied and one set of chromosomes are given to each new cell.

3. Meiosis 8 stages: Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II

4. Homologous Chromosomes Homologous Chromosomes are chromosomes that contain the same genes, but not necessarily the same alleles B b A A c c d D

5. Crossing Over Crossing over is a process in which different parts of homologous chromosomes switch places Crossing over leads to increased genetic recombination This occurs during Prophase I

7. II. Cell Division-Meiosis -Crossing over and the exchange of genes in meiosis is a major source of variation among organisms. In meiosis, you end up with 4 daughter cells that can be combined with another sex cell to make a new organism. MEIOSIS I MEIOSIS II Possible gametes Possible gametes Chromosome A Chromosome B Chromosome a Chromosome b

8. http://www.youtube.com/watch?v=pdJUvagZjYA&feature=related