Meiosis Chapter 10 Section 2 Diploid Haploid Cells

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Meiosis Chapter 10, Section 2

Meiosis Chapter 10, Section 2

Diploid & Haploid Cells Diploid = a cell with two sets of chromosomes, 2

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

Interphase and stages of mitosis

Interphase and stages of mitosis

Chromosomes from metaphase stage of mitosis

Chromosomes from metaphase stage of mitosis

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

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

MEIOSIS I Separation of homologous pairs Homologous Pair = in a diploid cell

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

1. Prophase I DNA coils into chromosomes Nuclear envelope & nucleolus break down

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

2. Metaphase I Tetrads line up in the middle of the cell Spindle

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

3. Anaphase I Each homologous chromosome moves to the opposite end of the

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

4. Telophase I & Cytokinesis I Two newly formed cells are haploid Each

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

MEIOSIS II Separation of sister chromatids Sister Chromatids = identical halves of a

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

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

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

6. Metaphase II Chromosomes line up in the center

6. Metaphase II Chromosomes line up in the center

7. Anaphase II Sister Chromatids separate

7. Anaphase II Sister Chromatids separate

8. Telophase II & Cytokinesis II 4 new cells, each with half the

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

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

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

Nondisjunction = failure of homologous pairs to separate in Meiosis I If an organism

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

Polyploidy Polyploid = organisms with more than the usual number of chromosome sets Occurs

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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