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Meiosis

Meiosis. Mitosis Review. Mitosis Video. Meiosis. Mitosis is the process by which normal cells divide in order for growth to occur. However , gametes (sex cells; sperm and egg) require a different process called meiosis . .

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Meiosis

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  1. Meiosis

  2. Mitosis Review • Mitosis Video

  3. Meiosis • Mitosis is the process by which normal cells divide in order for growth to occur. • However, gametes (sex cells; sperm and egg) require a different process called meiosis.

  4. Mitosis and meiosis differ in the number of chromosomes that are involved. • In mitosis, daughter cells are produced with the same number of chromosomes as the parent cell and there is one division of cytoplasm.

  5. In meiosis, daughter cells have half the number of chromosomes as the parent cell and there is two successive divisions of the cytoplasm.

  6. Haploid • The number of chromosomes in a gamete (egg or sperm) is called the haploid number of chromosomes or n.

  7. Diploid • Whereas all other body cells (somatic cells) have twice the haploid number of chromosomes and this is called diploid number of chromosomes or 2n. • In humans, the haploid number is 23, and the diploid number is 46.

  8. Video Time • Mitosis and Meiosis

  9. Why do we need meiosis? • Meiosis is the process whereby haploid gametes are produced. • This includes one replication of nuclear material and two back-to-back cell divisions. • This results in a possibility of forming four gametes or daughter cells. For humans, each sperm and egg cell would contain 23 chromosomes.

  10. Genetic Diversity • Meiosis produces gametes with unique chromosomal arrangements. • This is caused when homologous chromosomes synapse (process called synapsis). • Synapsis creates a pair of homologous chromosomes called a tetrad, because there are four chromatids.

  11. As the chromosomes pair, they often intertwine. • This is called crossing over and sometimes results in the exchange of genetic material between homologous pairs of chromosomes. • Therefore, four unique daughter cells are created.

  12. Meiosis Video • Meiosis Video

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