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Chromosomes and Cell Reproduction

Explore the intricacies of chromosomes, cell reproduction, mitosis, meiosis, and the cell cycle with detailed explanations and visuals. Learn about chromosome structure, cell division phases, and the significance of karyotypes in genetic analysis.

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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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