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Meiosis

Meiosis. Creating Gamete Cells. MEIOSIS : a process by which the number of homologous chromosomes per cell is reduced by half the number and is referred to as haploid cells ( n ). 46 chromosomes 23 pairs. Meiosis only happens in Gametes ( sex cells – egg or sperm ).

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Meiosis

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  1. Meiosis Creating Gamete Cells

  2. MEIOSIS: a process by which the number of homologous chromosomes per cell is reduced by half the number and is referred to as haploidcells (n).

  3. 46 chromosomes 23 pairs Meiosisonly happens inGametes ( sex cells – egg or sperm) Human female karyotype

  4. 46 chromosomes 23 pairs Human male karyotype

  5. What are homologous chromosomes? a similar pair of chromosomes, one from the father & one from the mother

  6. What is a Diploid Cell? A cell that contains 2 complete sets of homologous chromosomes issaid to bediploid or 2n Brain cells Blood cells Somatic(body cells) are diploid cells. Nerve cells Liver cells

  7. What is a Haploid Cell? A cell that contains 1 complete set of chromosomes. These are called gametes or sexcells(egg or sperm)

  8. Meiosis: production of gametes • Alternating stages • chromosome number must be reduced • diploid haploid • 2n n • humans: 46  23 • meiosisreduces chromosome number • makesgametes • fertilizationrestores chromosome number • haploid  diploid • n  2n haploid diploid

  9. Interphase I Prophase I Metaphase I Anaphase I Telophase I Metaphase II Telephase II and Cytokinesis There are 2 distinct divisions of meiosis: Meiosis I and Meiosis II resulting in 4 haploid daughter cells with “n” number of chromosomes

  10. Each chromosome pairs with its corresponding homologous chromosome to form a structure called a tetrad. Meiosis I - Prophase I There are 4 chromatids in a tetrad.

  11. I.P.M.A.T.P.M.A.T Overview of meiosis 2n = 4 interphase 1 prophase 1 metaphase 1 anaphase 1 n = 2 metaphase 2 anaphase 2 telophase 2 prophase 2 n = 2 telophase 1

  12. As homologous chromosomes pair up, they exchange genetic information in a process called crossing over producing new combinations of alleles – accounting for variation among species.

  13. JonasBrothers Baldwin brothers Martin & Charlie Sheen, Emilio Estevez Sexual reproduction creates variability Sexual reproduction allows us to maintain both genetic similarity & differences.

  14. 2n 2n 2n 2n 2n 2n n n n n n Gamete Formation in Meiosis Polar Bodies Sperm - male Egg- female

  15. Human Sperm + Human Egg Human Zygote 23 23 46 N N 2N Fertilization Mitosis Meiosis Cells Somatic (body) Gametes (sex) Examples Skin, Blood Sperm, Egg Chromosomes 2n n Found ? All over body Testes, Ovaries Cytokinesis Once Twice

  16. 2n 2n 2n 2n 2n 2n n n n n MITOSIS MEIOSIS

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