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Meiosis Chapter 10, Section 2.

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Presentation on theme: "Meiosis Chapter 10, Section 2."— Presentation transcript:

1 Meiosis Chapter 10, Section 2

2 Diploid & Haploid Cells
Diploid = a cell with two sets of chromosomes, 2n, somatic (body) cells muscle, skin, liver, etc. Haploid = a cell with one set of chromosomes, gametes, 1n, sperm and eggs Meiosis forms haploid gametes required for sexual reproduction Meiosis has 2 stages Meiosis I Meiosis II

3 Interphase and stages of mitosis

4 Chromosomes from metaphase stage of mitosis

5 Below are chromosomes after they split into chromatids during (telophase) of mitosis

6 Separation of homologous pairs
 MEIOSIS I Separation of homologous pairs Homologous Pair = in a diploid cell the 2 sets of chromosomes pair up

7  1. Prophase I DNA coils into chromosomes
Nuclear envelope & nucleolus break down Synapsis = homologous chromosomes pair up into tetrads Crossing-over = homologous pairs switch pieces of their chromatids Genetic Recombination = maternal & paternal genetic info get shuffled during crossing-over

8

9  2. Metaphase I Tetrads line up in the middle of the cell
Spindle fibers attach at the centromeres of each homologous chromosome

10

11  3. Anaphase I Each homologous chromosome moves to the opposite end of the cell Independent Assortment = random separation of chromosomes, allows for genetic variation

12

13  4. Telophase I & Cytokinesis I
Two newly formed cells are haploid Each chromosome is still made up of two chromatids

14

15 Separation of sister chromatids
 MEIOSIS II Separation of sister chromatids Sister Chromatids = identical halves of a chromosome that has been duplicated

16  5. Prophase II 2 newly created cells from Meiosis I start to divide

17  6. Metaphase II Chromosomes line up in the center

18  7. Anaphase II Sister Chromatids separate

19  8. Telophase II & Cytokinesis II
4 new cells, each with half the number of chromosomes of the original cell

20 Development of Gametes
Spermatogenesis = production of sperm cells Oogenesis = production of mature egg cells

21 Nondisjunction Nondisjunction = failure of homologous pairs to separate in Meiosis I If an organism survives, it may have a genetic disorder

22 Polyploidy Polyploid = organisms with more than the usual number of chromosome sets Occurs frequently in plants, results in plants that are larger than normal


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