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Cell Reproduction

Cell Reproduction. Chapter 8 Biology CPA. Chromosomes. Rod shaped structures made of DNA and proteins Chromosomes are visible in cells undergoing division Chromosomes are made by DNA coiling into tight structures Consist of two identical halves . Chromosome Structure.

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Cell Reproduction

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  1. Cell Reproduction Chapter 8 Biology CPA

  2. Chromosomes • Rod shaped structures made of DNA and proteins • Chromosomes are visible in cells undergoing division • Chromosomes are made by DNA coiling into tight structures • Consist of two identical halves

  3. Chromosome Structure • Histones are proteins that DNA wraps around to make the chromosome shape • Chromosomes are made of two sister chromatids • Identical to each other

  4. Chromosome Structure • Each chromosome is made of two “sister” chromatids • Near center of the chromosome is the centromere • Chromosomes are tightly coiled strings of DNA called chromatin

  5. Chromosome Numbers • There is a specific numberof chromosomes in each organism • Ex: Humans have 46, chimpanzees have 48 • Humans have autosomesand sexchromosomes • We have 2 sex chromosomes • Either X or Y • We also have 44 autosomes • Which do not code for gender

  6. Chromosome Numbers • Every cell of an organism produced by sexual reproduction has two copies of each autosome • One copy from mom and one copy from dad • The two copies of each pair is called homologous chromosomes • Same size and shape • Carry genes for the same traits

  7. Karyotype • A karyotype is a pictureof one set of chromosomes • Shows you sex of organism • Shows your any chromosomal disorders

  8. Chromosome Numbers • A diploidcell contains 2 sets of each chromosome • Prefix di = 2 • Abbreviated as 2n • n = number of chromosomes • A haploidcell contains only 1 set of each chromosome • Half of the total number • Usually sexcells

  9. Cell Division in Prokaryotes • Prokaryotes • No nucleus • No organelles • Ex: Bacteria • Reproduction is very fast • Copy DNA • Split into twoidentical daughter cells • Cell division is calledbinaryfission

  10. Cell Division in Eukaryotes • Eukaryotes • Have a nucleus • Have organelles • Ex: Humans, plants • Both nucleus and cytoplasm need to divide • Process of making new cells is called mitosis • Makes twoidentical daughter cells • Complex reproduction • Everything needs to be regulated! • Much more complex process – about 18 hours!

  11. Cell Division and Reproduction • Asexual Reproduction • Produces identicaloffspring from a singleparent • Used by many single-celled organisms • Ex: bacteria • Occurs very quickly • Sexual Reproduction • Produces genetically differentoffspring from two parents • Fusion of two parent cells • Creates haploidgametes (sex cells)

  12. The cell Cycle • A repeating set of events in the life of a cell • A cell splits to make 2 identicalcopies • This occurs in 3 main stages • Interphase – growth • Mitosis – divisionof the cell • Cytokinesis – Splitting of the cytoplasm

  13. Interphase • Cell growth • Majority of cell’s life span is spent in this phase • 3 Part of Interphase: • G1, S, G2

  14. G1 Phase • Gap 1 Phase • The cell is growing to mature size

  15. S Phase • S = synthesisof DNA • DNA is copiedso there is a set for each new cell

  16. G2 Phase • Gap 2 Phase • Cell growsagain • Replication of organelles • Cell prepares for cell division

  17. mitosis Cell Division

  18. mitosis • The part of a cell’s life cycle when the cell’s nucleus divides into 2 identicalnuclei • 4 steps: • Prophase • Metaphase • Anaphase • Telophase

  19. Prophase • Shortening and tight coiling of chromatin into chromosomes • Nucleus breaks down and disappears • Centrioles separate and move to opposite poles of the cell • Centrosomes in plant cells • Centrioles shoot off spindlefibers

  20. metaphase • Spindle fibers are connected to centromere of chromosomes • Spindle fibers move chromosomes • Chromosomes line up at the equator of the cell • Chromosomes are in the MIDDLE

  21. anaphase • Sister chromatids attach to the short spindlefibers • Chromatids of each chromosome separate at the centromere • Chromosomes are pulled APART • Spindle fibers shorten and bring the sister chromatids to oppositepoles • After chromatids separate, they are called individual chromosomes

  22. Telophase • Chromatids become chromatin • Spindle fibers disassemble • Nuclear envelope forms around each set of chromatin • Nucleolus reappears

  23. Cytokinesis • Once mitosis has finished! • Last stage of cellcycle • Process is when the cytoplasm splits apart

  24. Cytokinesis in Plant Cells • A cellplateforms between the two nuclei • The cytoplasm divides • A cellwallforms two daughter cells

  25. Cytokinesis in Animal Cells • Cell membrane pinches in at equator • Cleavage furrow

  26. Cells in Various Stages of the Cell Cycle

  27. Control of Cell Division • Checkpoints (Regulatory Proteins) • Repair enzymes fix any mutations • G1 Checkpoint • Proteins check to see if cell will be able to divide • Check for cell size • G2 Checkpoint • DNA repair enzymes check results of DNA replication during S phase • Mitosis checkpoint • If all is correct, proteins will signal cell to exit mitosis • Cell will renter interphase after cytokinesis and start process over again • If a cell does not meet requirements for checkpoints, the cell will be programmed to die • Apoptosis is controlled cell death

  28. Uncontrolled Mitosis is cancer.

  29. When Control is Lost • Enzyme proteins are not functioningproperly causing cell to reproduce outofcontrol • Could cause cancer • Cancer cells do not respond to body’s regulators that control mechanisms • A mass of cancer cells is called a tumor

  30. Compare/Contrast

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