Meiosis Chapter 10 Section 2 Diploid Haploid Cells

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

Chromosomes from metaphase stage 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

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

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

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

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

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

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

6. Metaphase II Chromosomes line up in the center

7. Anaphase II Sister Chromatids separate

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

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

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

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

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Meiosis Chapter 10, Section 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

Chromosomes from metaphase stage 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 the 2 sets of chromosomes pair up

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 fibers attach at the centromeres of each homologous chromosome

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 chromosome is still made up of two chromatids

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

6. Metaphase II Chromosomes line up in the center

7. Anaphase II Sister Chromatids separate

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 egg cells

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 frequently in plants, results in plants that are larger than normal