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Chromosomes and Cell Reproduction

Chromosomes and Cell Reproduction. Chapter 6 & 7. I. Chromosomes. Chromosome- made of 2 exact copies of DNA coiled around proteins (*this is after replication but before cell division ) Chromatid- each copy of the DNA on a chromosome

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Chromosomes and Cell Reproduction

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  1. Chromosomes and Cell Reproduction Chapter 6 & 7

  2. I. Chromosomes • Chromosome- made of 2 exact copies of DNA coiled around proteins (*this is after replication but before cell division) • Chromatid- each copy of the DNA on a chromosome • Centromere- place where the chromatidsattach to make a chromosome • Genes- Segments of DNA on a chromosome that code for a specific protein/trait

  3. *Draw a chromosome and label chromatids, centromere and gene

  4. II. Chromosome Number • Each human somatic cell (body cell) has 2 copies of 23 different chromosomes for a total of 46 chromosomes • We inherit 1 of each chromosome from mom and 1 from dad • Homologous Chromosomes- similar in size, shape and genetic content

  5. D. Diploid cells- contain 2 sets of chromosomes, all somatic cells are diploid (ex. Somatic cells in humans have a total of 46 chromosomes) E. Haploid Cells- contain only 1 set of chromosomes, only gametes can be haploid (ex. Gametes in humans have 23 chromosomes)

  6. III. Karyotypes • A picture of the chromosomes of an organism arranged by size • Used to examine an individuals chromosomes: • Karyotypes can determine only 2 things about the organism: • Sex of individual • Any abnormalities in the chromosomes (number or shape

  7. C. Humans have 1 pair of sex chromosomes and 22 pairs of autosomal chromosomes (non sex chromosomes) D. Sex Chromosomes- XX= Female XY= Male (the sex chromosomes are the last pair of chromosomes shown in a karyotype)

  8. Trisomy – when there is three of a certain chromosome instead of the normal 2

  9. IV. Cell Cycle • G1 Phase- period of cell growth • S Phase- when DNA replication occurs • G2 Phase- cell growth and preparation for mitosis • Mitosis- division of the nucleus • Cytokinesis- division of the cytoplasm

  10. Cell Cycle Animations http://www.cellsalive.com/cell_cycle.htm • http://iknow.net/cell_div_education.html

  11. V. Mitosis • The division of the nucleus in somatic cells • Chromosomes have replicated prior to the start of mitosis • Produces 2 identical daughter cells • 4 phases

  12. Prophase- • chromatin coils into chromosomes • Nuclear envelope dissolves • Spindle fibers form

  13. 2. Metaphase (middle) • Chromosomes line up in the middle of the cell • Centrioles move to opposite poles • Spindle fibers attach to chromosomes

  14. 3. Anaphase (apart) • Spindle fibers shorten and pull chromatids toward opposite poles

  15. 4. Telophase (opposite of prophase) • Nuclear envelope forms around chromatids • Chromatids uncoil • Cleavage is formed • Spindle fibers dissolve

  16. E. Cytokinesis • Occurs after Mitosis • Cytoplasm is divided in half • Cell membrane encloses each cell **New cells are now in interphase and the cell cycle starts over.

  17. Mitosis Animation • http://iknow.net/cell_div_education.html http://www.loci.wisc.edu/outreach/bioclips/CDBio.html

  18. VI. Meiosis • Two divisions of the nucleus • Results in the formation of 4 gametes (egg, sperm) • Halves the number of chromosomes (in humans from 46 to 23)

  19. Stages of Meiosis I 1.*Prophase I- crossing over occurs, (portions of one chromosome are broken and exchanged with portions of the other homologue)**results in genetic variability 2. Metaphase I- homologous chromosome pair up together at the equator 3. Anaphase I- centromeres do not divide 4. Telophase I and Cytokinesis

  20. Meiosis II 1. Prophase II 2. Metaphase II 3. Anaphase II 4. Telophase II & Cytokinesis http://www.tokresource.org/tok_classes/biobiobio/biomenu/meiosis/ Interphase A 1 P 1 M 1 T1 & C P 2 M 2 A 2 T 2 Cytokinesis

  21. Females- called oogenesis, forms 1 ovum and 3 polar bodies Males- called spermatogenesis, forms 4 sperm cells

  22. http://www.biologyexams4u.com/2013/06/difference-between-spermatogenesis-and.htmlhttp://www.biologyexams4u.com/2013/06/difference-between-spermatogenesis-and.html

  23. Meiosis Animations Meiosis Animation Meiosis Square Dance Video

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