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Cellular Reproduction

Cellular Reproduction. Why Cells Reproduce/Divide. Growth Cell Repair Cell Replacement. Why do cells multiply and not just grow bigger?. DNA overload : -the DNA can handle only so many requests for ‘information’ ex: library in growing town 2. Exchange of materials :

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Cellular Reproduction

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  1. Cellular Reproduction

  2. Why Cells Reproduce/Divide • Growth • Cell Repair • Cell Replacement

  3. Why do cells multiply and not just grow bigger? • DNA overload: -the DNA can handle only so many requests for ‘information’ ex: library in growing town 2. Exchange of materials: -the cell must have enough surface area (cell membrane) to transport waste and nutrients into/out of cell -cells need HIGH surface area to volume ratio

  4. Ratio of Surface Area to Volume in Cells 3:1 2:1

  5. -if a cell gets too large, it is difficult to get sufficient amounts of oxygen and nutrients in and out of cell -this is why cells do not grow much even if the organism they are a part of does

  6. -before it gets too large, a growing cell divides forming two daughter cells -called cell division -before the cell divides, it replicates(copies) all of its DNA -helps with information b/c each daughter cell gets its own genetic info

  7. Chromosomes -carry genetic info -condensed form of DNA and protein -only visible during cell division b/c they come together -are copied before cell division to get two sister chromatids -chromatids are attached by centromeres -most human cells have 46 chromosomes (each with 2 sister chromatids)

  8. -a duplicated chromosome has two sister chromatids which become divided during mitosis and are distributed to each daughter cell

  9. Cell Cycle -the series of events that cells go through as they grow and divide into two daughter cells -occurs in all cells (except sex cells) -every 20 hours in humans

  10. Phases of the Cell Cycle INTERPHASE -longest phase of the cell cycle *G1: cell growth/making of organelles *S: chromosomes are copied to prep for mitosis (DNA replication) *G2: making of more organelles in prep for M phase, shortest phase of interphase

  11. CELL DIVISION *M: division of the nucleus (mitosis) and the cytoplasm (cytokinesis) occurs -made up of five total steps

  12. Interphase -longest part of the cell cycle -3 distinct parts  G1, S, G2 -cell increases in mass -number of organelles doubles -DNA is duplicated

  13. Interphaselooks like: • Nucleus and nucleolus visible. chromatin nuclear membrane cell membrane nucleolus

  14. same chromosomes (duplicated) in interphase prior to mitosis mitosis, cytoplasmic division chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in daughter cell at interphase chromosomes (unduplicated) in parent cell at interphase Maintaining Chromosome Number

  15. Mitosis – Division of the nucleus Made up of 4 smaller phases: • Prophase • Metaphase • Anaphase • Telophase *can last from a few minutes to a few days

  16. Prophase • longest of the 4 stages (50% of the time) • nucleus and nucleolus disappear • chromosomes become visible • centrioles appear and separate • spindle fibers gap the space in between the two centrioles

  17. The Spindle Fibers -a web type structure made up of microtubule fibers -is essential for mitosis because it arranges the chromosomes into their correct positions to prep for cell division. Mitotic centre A cell atmetaphase a spindle Microtubule

  18. Metaphase • shortest phase (only a few minutes) • chromosomes line up along the center of the cell • centromeres attach to spindle fibers

  19. Anaphase • centromeres split • chromatids move towards the separate poles (centrioles)

  20. Telophase • chromosomes become invisible again • 2 distinct nuclei form

  21. CYTOKINESIS: the separation of the cytoplasm between the two daughter cells • begins during anaphase and usually extends past • animal cells: -membrane pinches in on both sides until they meet in the center • plant cells: -a cell plateforms (becomes new cell wall)

  22. Animal Cell Division

  23. vesicles converging Plant Cell Division cell wall former spindle equator cell plate

  24. REVIEW:

  25. Mitosis

  26. Mitosis Part One

  27. Mitosis Continued

  28. Mitosis Song

  29. Cell Division Regulation: • internal regulators: determine when phases occur ex: cyclin protein • external regulators: respond to events outside cell ex: hormones • uncontrolled growth is known as cancer

  30. Meiosis -a process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell homologous pairs- each chromosome set has one from male and one from female parent

  31. diploid- has both sets of homologous chromosomes haploid- has one set of chromosomes diploid (2N)  haploid (N) diploid = full set of chromosomes haploid = half set of chromosomes

  32. -meiosis produces 4 haploid gamete cells from one diploid cell gametes cells- sex cells (egg and sperm)

  33. -two rounds of cell division in meiosis -this is how the amount of chromosomes gets cut in half -homologous chromosomes are separated

  34. Meiosis I -first round of division -homologous chromosomes separated Meiosis II -second round of division -chromosome number cut in half

  35. MEIOSIS I and II

  36. MEIOSIS I -similar to mitosis: *cell prepares for division *DNA is replicated BUT: *homologous chromosomes pair up *form a tetrad- made up of 4 chromatids **called synapsis *exchange portions of their genes *called crossing over (this adds to diversity)

  37. MEIOSIS II -no interphase II (no more DNA replication) -very similar to mitosis -chromosomes line up as individuals, have already been separated from partner -sister chromatids split

  38. PROPHASE II

  39. METAPHASE II

  40. TELOPHASE II and CYTOKINESIS

  41. During meiosis: -chromosomes independently assort (separation of genes during gamete formation) -haploid gametes in men = sperm cell -haploid gametes in women = egg cell *other three cells (in females) are called polar bodies

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