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Cell Reproduction and Division Ch 8

Cell Reproduction and Division Ch 8. Chromosomes. Chromosome : DNA wrapped up w/ histones (proteins) = organized Chromatin : uncoiled chromosome= unorganized DNA. Chromosome #. All species have their own characteristic # of chromosomes in each cell. Chromosome Number.

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Cell Reproduction and Division Ch 8

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  1. Cell Reproductionand DivisionCh 8

  2. Chromosomes • Chromosome: DNA wrapped up w/ histones (proteins) = organized • Chromatin: uncoiled chromosome= unorganized DNA

  3. Chromosome # • All species have their own characteristic # of chromosomes in each cell

  4. Chromosome Number • Diploid 2n: pairs of chromosomes (1 from each parent • Haploid 1n: unpaired chromosomes (sperm or egg)

  5. Chromosome Terminology Centromere 1 Chromosome With 2 chromatids (duplicated) 1 Chromosome Centromere 2 chromosomes (both duplicated) If these are homologous it is a tetrad 2 chromosomes (Unduplicated)

  6. Chromosome Types SEX CHROMOSOMES Determine Gender • Males: XY • Females: XX • Male determines gender of the baby AUTOSOMES • All non-sex chromosomes

  7. How many C’somes do you have? • Humans: 23 pair = 46 chromosomes • Karyotype: arrangement of an individuals chromosomes

  8. Homologous Chromosomes • Have the same type of information but with different details • #2 from mom has same kind of info as #2 from dad • Which ones aren’t homologous?

  9. Haploid/Diploid

  10. 25Cell Division

  11. Cell Division in Prokaryotes • Binary Fission-Bacterial Cells reproduce asexually

  12. Mitosis & Cell Division In Eukaryotes • When a cell gets too big, it divides or stops growing • Eukaryotes first divide nucleus =Mitosis, then divide the rest =cytokinesis

  13. Cell Cycle • A cells life is divided into a cycle • Interphase, Mitosis & Cytokinesis are steps in the cycle

  14. Stages of the cell cycle • INTERPHASE = most active & majority of time • G1 stage = "GAP 1” - intense growth • Sstage = "Synthesis” • DNA replication occurs-IT DOUBLES! • G2 stage = "GAP 2” - duplicate organelles • G0 stage = exit cycle & never divide again (CNS=nerve cells) • MITOSIS • M stage = mitosis - nucleus divides • Divided into PMAT • Cytokinesis= cell divides

  15. Interphase • The cell is metabolizing, growing and preparing for mitosis • Chromosomes are not clearly seen • Where a cell spends most of its life

  16. Controlling the Cell Cycle • Length varies • 3 checkpoints based on proteins • G1, G2 and Mitosis • Errors can lead to cancer. • In cancer, regulation of the cell cycle is lost • Normal cell growth & behavior is lost.

  17. What is Mitosis? • Nuclear division • Produces two identical daughter cells during prophase, metaphase, anaphase, and telophase (PMAT).

  18. Prophase= PREPARE for division, chromosome PRESENT • Chromatin begins to condense and c’some becomes visible. • Spindle fibers form

  19. Prophase (cont.) • Nuclear membrane dissolves • Microtubules form mitotic spindle • Kinetochore fibers and polar fibers attach to centromeres

  20. Metaphase-in MIDDLE • Spindle fibers align the chromosomes in the center or equator of the cell • Helps to ensure each new nucleus will receive one copy of each chromosome.

  21. Anaphase-Chromatids APART • Chromatids separate and move to opposite sides • Spindle fibers break down • Once separate they are called chromosomes

  22. Telophase-almost TWO cells • Chromosomes arrive at opposite poles • Nuclear envelope re-forms around daughter nuclei. • Chromosomes uncoil • Spindles disappear

  23. Cytokinesis in Animal Cells • Cytoplasm is pinched (cleavage furrow) into two daughter cells

  24. Plants • In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

  25. Meiosis - formation of gametes

  26. Sexual Reproduction • Sex cells divide by meiosis to produce haploid gamete (half the number of chromosomes) • Gametes will join & fertilize • Meiosis produces 4 gametes that are slightly different in genetic makeup from each other • Two gametes join to form 1zygote

  27. Meiosis IReduces number of chromosomes by half (diploid to haploid) PMAT I’s – separate homologous pairs • Meiosis II: Separates the sister chromatids PMAT II’s

  28. Meiosis I

  29. Meiosis II

  30. Prophase I: • Synapsis (pairing of homologous c’somes) • When crossing-over happens (genetic recombination)

  31. Crossing over: during Meiosis I Homologous pairs form tetrads, cross over and separate into individual chromosomes • Homologous c’somes exchange genetic material • Important for genetic diversity

  32. Prophase I Each tetrad has two chromo- somes & four chromatids

  33. Meiosis • Spermatogenesis: production of sperm cells • Oogenesis: production of egg cells

  34. Comparing Meiosis & Mitosis Genetic identity of progeny • Meiosis • Daughter cells have new assortment of parental chromosomes • Chromatids not identical; crossing over • Diploid to haploid • 1 cell  4 • Mitosis • Identical daughter cells • diploid • 1 cell  2

  35. Sexual Reproduction • Formation of offspring through meiosis and the union of a sperm and an egg (zygote) • Offspring are genetically different from parents

  36. Independent Assortment • Anaphase I – homologous chromosomes separate from each other • Mendel figured this out

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