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Meiosis with Mitosis Review and Comparison (Chapters 8 and 10)

Meiosis with Mitosis Review and Comparison (Chapters 8 and 10). Recall Mitosis. ** Mitosis is asexual reproduction & occurs ONLY in regular old body cells called SOMATIC CELLS (skin, nails, your pancreas, etc..) NOT sperm and eggs  ** Produces two identical diploid (2n) cells.

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Meiosis with Mitosis Review and Comparison (Chapters 8 and 10)

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  1. Meiosis with Mitosis Review and Comparison (Chapters 8 and 10)

  2. Recall Mitosis ** Mitosis is asexual reproduction & occurs ONLY in regular old body cells called SOMATIC CELLS (skin, nails, your pancreas, etc..) NOT sperm and eggs  ** Produces two identical diploid (2n) cells

  3. Diploid Chromosomes • We call somatic cells diploid (2n) meaning you have 2 copies of each chromosome (1/2 from mom and ½ from dad) • Autosomalchromosomes are non-sex chromosomes • These contain genes that have nothing to do with determining your sex • Each of your cells contain 44 autosomal chromosomes and 2 sex chromosomes (XX for female and XY for male) for a total of 46 chromosomes in each nuclei of your cells

  4. Cell Cycle – Diploid (2n), Somatic Cells (Body Cells)

  5. Mitosis Produces Identical, Diploid Daughter Cells (46 chromosomes in the nuclei of the cells) Replicates Above are Homologous Chromosomes - Same chromosome with same types of genes on each chromosome, just different variations from each parent

  6. Meiosis and The Human Life Cycle FROM MOM FROM DAD

  7. Meiosis Overview **Diploid cells divide twice to produce haploid (n) sperm or egg (each have 23 chromosomes) **Required for Sexual Reproduction • **Produced in the ovaries (females) and testes (male) • **Results in 4 NON-IDENTICAL haploid (n) cells • Genetic recombination creates genetic variability in either sperm or egg • For each meiotic division, 4 sperm are produced but typically only 1 egg survives

  8. Meiosis Phases • **After interphase (DNA replication phase) • **Meiosis I Prophase I, Metaphase I, Anaphase I, telophaseI • **Meiosis II Prophase II, Metaphase II, Anaphase II, Telophase II and cytokinesis • **4 cells, the gametes!!

  9. Fertilization • When egg and sperm fuse we say the egg is fertilized creating one, single diploid cell called a zygote Although numerous sperm attempt to fertilize the egg, only one will succeed Diploid zygote – will undergo mitosis

  10. Sex Chromosomes Male = XY Female = XX

  11. Meiosis occurs in 2 phases. Meiosis 1 and Meiosis 2 with cytokinesis following. The process results in 4 non-identical haploid cells After Meiosis 2 occurs the result is 4, non-identical haploid sperm or egg cells called gametes After Meiosis 1 From your From your Dad Mom Replication Homologous chromosomes – SAME chromosome type (have the same types of genes) A tetrad is formed Crossing Over between non-sister chromatids During Prophase 1 of Meiosis 1 – Results in genetic recombination

  12. Meiosis I

  13. Meiosis II

  14. Genetic Recombination

  15. Genetic Recombination During Meiosis ** A reassortment of chromosomes and genetic information they carry **crossing over between non-sister chromatids during Prophase 1 **independent assortment of homologous chromosomes

  16. Crossing Over **Pink is from your mom, blue from your dad **Non-sister chromatids exchange genetic information

  17. Sister Chromatids of Homologous Chromosomes Cross Over

  18. Independent Assortment leads to genetic variability- homologous chromosomes are sorted before shipment to gametes independently of how the other pairs were sorted

  19. Meiosis Square Dance

  20. Problems During Meiosis

  21. Non-Disjunction **chromosomes of a homologous pair (tetrad) fail to separate and move to the same pole of the cell. Some gametes may have an extra chromosome while others lacking ** Down syndrome occurs because of this. Called trisomy 21, there are 3 of chromosome #21 rather than a pair!

  22. Karyotypes – Pictures of a person’s Chromosomes – Show Abnormalities Male with no chromosomal abnormalities

  23. Abnormal Karyotype Trisomy 18 – Due to Non-disjunction

  24. Compare Mitosis to Meiosis

  25. Mitosis (asexual reproduction) vs. Meiosis (sexual Reproduction) • Meiosis • Occurs in 2 stages • Produces 4 genetically different haploid cells (genetic recombination) • For Sexual Reproduction • Produces genetically variability due to recombination • Occurs in sex cells called gametes or germ cells and four haploid cells (sperm and egg) • n=23  22 autosomal chromosomes and 1 sex chromosome • Forms a tetrad • Mitosis • Occurs in 1 stage • Produces 2 genetically identical diploid cells • It is Asexual Reproduction • Produces “clones” with no genetic variability • Occurs in body cells (autosomal) and creates two diploid cells • 2n=46  22 pair of autosomal chromosomes and 1 pair sex chromosomes

  26. Meiosis Mitosis

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