Cell Cycle - PowerPoint by kZ2ubZ


									             Explain the following:
"It  is not a simple life to be a single
 cell, although I have no right to say
 so, having been a single cell so long
 ago myself that I have no memory at
 all of that stage of my life."
 —Lewis Thomas (1913–1993) author,
 biologist, physician
Cell Cycle
                   The Cell Cycle
A   period of growth, DNA replication and
  cell division that MOST cells go through
 Examples of cells that don’t: nerve, brain and muscle
 Examples of cells that do: blood, intestinal and skin
           Blood cells-2.4 million per second

Cell       Cycle is divided into 3 phases
                                                                           A typical animal cell cycle lasts roughly 24 hours,
but depending                                                             on the type of cell, it can vary in length from less
                                                       than 8 hours to more than a year. Most of the variability occurs in G1.

 This   cycle begins when the cell is produced by
    mitosis and runs until the cell undergoes its own
    mitosis and splits in two.. As you can see, mitosis
    only occupies a fraction of the cycle. The rest of
    the time-phases G1 through G2—is known as

   http://publications.nigms.nih.gov/insidethecell/chapter4.html#10
             The Cycling Cell
 Scientists used to think of interphase as a resting phase
  during which not much happened, but they now know that
   this is far from the truth. It is during interphase that
  chromosomes—the genetic material—are copied and cells
    typically double in size. While this is happening, cells
 continue to do their jobs: Your heart muscle cells contract
  and pump blood, your intestinal cells absorb the food you
 eat, your thyroid gland cells churn out hormones, and so on.
  In contrast, most of these activities cease during mitosis
 while the cell focuses on dividing. But as you have probably
 figured out, not all cells in an organ undergo mitosis at the
same time. While one cell divides, its neighbors work to keep
                    your body functioning.
               http://publications.nigms.nih.gov/insidethecell/chapter4.html#10
 Longest phase of the cell cycle
 Consists of 3 distinct periods
G1    phase
 Proteins  are produced, organelles
  increase (multiply)
 Cells grow during this phase, increase in
 Cells acquire ATP (energy) for later use
S   phase
DNA   synthesis (DNA is replicated)
G2         phase
Changes  in cytoskeleton to prepare cell
 for mitosis
Cell undergoes more growth
Cell acquires more energy (ATP)
Nucleolus  is present
Individual chromosomes are NOT
 visible (DNA is known as chromatin)
Nuclear membrane is present
Nuclear      division, it is the process of
    forming identical daughter cells by
    replicating and dividing the original
    chromosomes, in effect making a
    cellular Xerox copy.
   http://highered.mcgraw-
Prophase: 1st stage of mitosis
Chromatin  forms chromosomes (chromosomes
 become visible)
Centrioles separate, start to move to opposite
Spindle fibers form
Nuclear envelope (membrane) breaks down
Spindle fibers attach to centromeres

Referred   to as “sister” chromatids
  Metaphase: 2nd stage of
Chromosomes     move to center of the cell
 and line up in the middle of cell
Site where chromosomes gather is
 called the metaphase plate
Anaphase: 3rd stage of mitosis
 Shortest  stage of mitosis
 Spindle fibers pull apart chromatids
 Chromatids move to opposite ends of
  the cell
Telophase: 4th stage of mitosis
 End  of mitosis (terminal stage)
 Spindle fibers (disassemble) break
 Nuclear envelope re-forms around
 Chromosomes begin to break apart
 Two identical nuclei exist in the cell
 Nucleolus starts to re-form
Division   of cytoplasm following mitosis

Results    in two daughter cells

Animal   cells?

Plant   cells?

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