Mitosis

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Mitosis The Cell Cycle

• The 5 phases of the cell.

2
Refresher on DNA

• DNA is the master molecule of the cell. DNA is
  located in the nucleus of nearly every cell.

http//www.3dscience.com/img/Products/3D_Models/Bi
ology/DNA/DNA_w_Phosphate_structure/Supporting_ima
ges/3d_model_DNA_w_phosphate_1.jpg
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DNA
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Refresher on DNA

• Genes are sections of DNA that are typically
  about 5000 nucleotides long. Genes are the
  directions for making a certain kind of protein
  for the cell.

http//z.about.com/d/p/440/e/f/9344.jpg
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DNA
Gene
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Refresher on DNA

• Chromosomes are rod-shaped structures that
  contain long sections of DNA with hundreds of
  genes. Chromosomes can only be seen right before
  and during cell division.
• During the other phases of the cells life, the
  DNA uncoils somewhat and exists as chromatin
  which is not visible with a light microscope.

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DNA
Gene
Chromosome
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Chromosomes vs. Chromatin
http//images.google.com/images?gbv2svnum10hl
enqnucleusTEMchromatin
http//www.microscopy-uk.org.uk/mag/imgnov04macro/
metaphase.jpg
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Human Chromosomes (46)
http//131.229.114.77/microscopy/images/Chromosome
s2.jpg
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Development of an Embryo

• The adult human body contains an estimated 100
  trillion cells. Therefore, we are considered to
  be multicellular organisms.

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Development of an Embryo

• DNA is extremely important! DNA molecules are
  needed to store the directions on how to make new
  cells and to tell those new cells what their
  function within the body will be. However, every
  cell in the body has identical DNA.

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Differentiation

• If every cell has identical DNA, why dont all of
  the cells look and act the same? Because not all
  of the DNA is used. Various sections of the DNA
  are activated from one type of cell to the next.
• This process of creating different cells using
  identical DNA is called differentiation.

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Cell Division
Activation of certain genes
Differentiation
http//scienceblogs.com/clock/upload/2006/12/a220
cell20differentiation.gif
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Differentiation

• So when, and how does a cell develop and
  differentiate? The process begins with the cell
  cycle.
• Recall that all of us started out as one cell, a
  combination of egg and sperm. During
  development, cells first divide and later will
  begin to differentiate to form various body parts.

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The Cell Cycle

• As we develop, our cells go through a cycle of
  events. The basic cell cycle looks like this

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Phases of the Cell Cycle

• M Mitosis ( cell division) or sometimes
  Meiosis (making of gametes/sex cells).
• G1 Gap 1 During this phase cells are not
  resting! They are busy making proteins, breaking
  down toxic molecules, and using energy.
• S DNA replication or synthesis. During this
  phase the cell must make an extra copy of DNA to
  prepare for mitosis.
• G2 Gap 2 During this phase cells are again not
  resting! They are busy preparing for cell
  division.

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Differentiation

• At first, cells go through the cell cycle rapidly
  and do not have time to differentiate, but at
  some point in development the cells stop dividing
  and begin to differentiate into different types
  of cells. (In other words, they remain in the G1
  phase.)

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Differentiation

• Some cells in the human body divide our entire
  lifetime. Our hair follicles, skin, and the
  lining of our digestive tract are examples of
  cells that constantly divide. These cells are
  fairly simple and mainly serve as barriers or
  boundaries.

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Differentiation

• Some cells completely lose their ability to
  divide. Once they differentiate, they can no
  longer go back to this cycle. Muscle cells and
  cells of the central nervous system cannot be
  replaced once they are destroyed because of this.

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Differentiation

• Some cells remain in the G1 phase most of the
  time. They can regain their ability to divide
  temporarily in order to replace damaged cells,
  but will then go back into a mode of not dividing.

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Differentiation (or lack of)

• Cancer a simplified explanation of cancer cells
  is that these are cells that have gone into a
  rapid, repetitive cell cycle. Cells normally
  have mechanisms to prevent this from happening,
  but if a number of these preventative measures
  fail, cells can begin to multiply uncontrollably.
  Cancer cells do not have time to differentiate.
  They look different, do not function normally,
  and eventually squeeze out the normal cells that
  surround them. Cancer cells have a cell cycle
  thats gone bad!

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The 5 phases of the cell

• There are 5 recognizable phases of the cell
  IPMAT
• I Interphase
• P Prophase
• M Metaphase
• A Anaphase
• T Telophase

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Interphase

• Interphase includes the G1, S, and G2 cell cycle
  phases.
• Cells spend most of their time in interphase.
  The only time that a cell can be seen in one of
  the other 4 phases is when the cell is in the
  process of dividing.

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Mitosis

• Mitosis is paired with cell division
• Mitosis refers to the process when the
  chromosomes divide.
• Cell division often refers to the process when
  the remainder of the cell (cytoplasm) divides,
  but this term can be used more generally as well.
• Mitosis includes prophase, metaphase, anaphase,
  and telophase.

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Interphase most of the time the cell looks like
this.
Mitosis The 4 phases of mitosis can be easily
identified using a microscope.
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1

• Which of these is prophase, metaphase, anaphase,
  telophase, and interphase?

http//www.sep.alquds.edu/biology/scripts/Biology_
english/part_3_4_files/image010.jpg
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2

• Is this interphase, prophase, metaphase,
  anaphase, or telophase?

http//biology.nebrwesleyan.edu/benham/mitosis/ima
ges/alliumtelophase.JPG
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3

• Is this interphase, prophase, metaphase,
  anaphase, or telophase?

http//www.instr.science.ru.nl/lichtmicroscoop/bf-
division.jpg
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4

• What phase is this?

http//www.instr.science.ru.nl/lichtmicroscoop/bf-
division.jpg
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5

• What phase is this?

http//chsweb.lr.k12.nj.us/psidelsky/onion_root_ti
p__1000_X__-10.jpg
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6

• What phase is this?

http//kcfac.kilgore.cc.tx.us/kcap1/images/whitefi
sh20mitosis20telophase201000x2020fireworks.jp
g
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7

• What phase is this?

http//virtual.yosemite.cc.ca.us/randerson/Lynn's
20Bioslides/86.jpg
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8

• What phase is this?

http//virtual.yosemite.cc.ca.us/randerson/Lynn's
20Bioslides/94.jpg
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9

• What phases are these?

E
A
G
C
F
D
H
B
http//www.phschool.com/science/biology_place/labb
ench/lab3/images/anifield.gif