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DNA and Cell Division

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Title: DNA and Cell Division


1
DNA and Cell Division
2
Mitosis in Animals
3
Background Information
Once an egg becomes fertilized, cellular
divisions begins, eventually producing a whole
organism
All cells derived from the zygote contain the
same genetic material
An Integrated Organism
4
Organization of DNA
  • All cells have DNA (chromosomes).
  • Almost all cells divide for reproduction, growth
    or repair.
  • Each new cell needs the exact same DNA as the
    original cell.
  • The original cell is called the mother cell and
    the two new cells are called daughter cells.
  • The DNA in the nucleus must replicate before the
    cell divides.

5
Chromosome Number in Different Species
Common Name Genus and Species Diploid ChromosomeNumber
Buffalo Bison bison 60
Cat Felis catus 38
Cattle Bos taurus, B. indicus 60
Dog Canis familiaris 78
Donkey E. asinus 62
Goat Capra hircus 60
Horse Equus caballus 64
Human Homo sapiens 46
Pig Sus scrofa 38
Sheep Ovis aries 54
6
Number of genes in sequenced genomes
  • E. coli 4300
  • Yeast 6000
  • Roundworm 18,600
  • Fruit fly 13-14,000
  • Mosquito 13-14,000
  • Mouse 30-35,000
  • Human 30-35,000

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A non-dividing cell
  • 90 of a cells life is spent growing, not
    dividing
  • This phase is called interphase
  • The DNA in this phase is not condensed thus is
    chromatin
  • At some point during this phase the DNA is
    doubled or replicated
  • Two copies are made, one for each of the new
    cells

9
  • Once replication occurs, the chromatin folds up
    to form chromosomes
  • This only occurs when the cell is about to divide
  • The duplicated chromosomes attach to each other
    at the centromere
  • Each individual copy of one chromosome is known
    as a chromatid
  • When chromatids are joined at the centromere,
    they are known as a single chromosome.

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sister chromatids
centromere
A piece of DNA or chromosome in an undividing
cell
Same piece now has replicated and super coiled
ready for cell division.
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Also during interphase
  • Additional organelles are produced
  • Cell membrane enlarged to allow cell growth
  • When the cell becomes too big to function it must
    divide
  • What would the SA/V ratio of this cell belarge
    or small?

14
Interphase
  • The cell grows
  • New organelles are formed
  • Duplicate chromosomes are produced
  • The chromosomes are uncoiled and invisible
  • This uncoiled chromosomes are known as a
    chromatin

15
Cell division/reproduction
  • Interphase is not considered to be part of cell
    reproduction.
  • It is simply the growth of the cell and the
    duplication of the chromosomes.
  • Cell reproduction consists of two separate stages
    known as mitosis and cytokinesis.
  • Cell division mitosis cytokinesis
  • A parent cell will produce 2 daughter cells.

16
In cell division each chromosome is replicated
and then the cell (and nucleus) divides
17
Cell Reproduction
  • Original cell divides into two genetically
    identical daughter cells
  • Complete set of genetic information passed onto
    each daughter cell
  • DNA must be accurately duplicated before cell
    division
  • Mitosis paired chromatids separate and move to
    opposite ends of the cell
  • Cytokinesis cytoplasm organelles divide into
    roughly equal halves

18
http//www.stolaf.edu/people/giannini/flashanimat/
celldivision/crome3.swf
Mitosis Animation
19
MITOSIS/ CELL DIVISION
  • Stages include
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase

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Mitosis
Nucleolus disappears Nuclear envelope breaks down
Chromosomes condense and shorten
Duplicated chromosomes remain elongated
LateInterphase
EarlyProphase
LateProphase
Metaphase
Centromeres align at cells equator
Microtubules attach to Centromeres
Centrioles have also been duplicated
Centrioles begin to move apart Spindle forms
22
Mitosis
Spindle fibers pull chromatids to opposite poles
Cytoplasm divided along equator
Chromosomes begin unwinding
NextInterphase
Anaphase
Telophase
Cytokinesis
Nuclear envelope re-forms, spindle fibres
disappear
Each daughter gets 1 nucleus half of cytoplasm
Chromatids become independent chromosomes
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Prophase
  • Chromatin condenses (into chromosomes)
  • Chromosomes appear as Xs.
  • Nuclear envelope dissolves (DNA free in cell)
  • Animals cells only Centrioles move to opposite
    ends of cell form spindle fibers
  • Centromere attaches to spindle fibre

26
Metaphase
  • Each chromosome lines up in the middle of the
    cell.
  • Highly organized so that both cells get exactly
    the same DNA.
  • Spindle fibers attached to centromeres of
    chromosomes

27
Anaphase
  • Each pair of chromatids splits at the centromere
  • Each chromatid is now an individual chromosome
  • Paired chromosomes are pulled to opposite ends by
    spindle fibres

28
Telophase
  • Chromosomes end up at separate poles, spindle
    fibers begin to dissolve.
  • New nuclear envelope begins to form around
    chromosomes
  • chromosomes begin to uncoil
  • Cell starts to pinch off through cytokinesis

29
Cytokinesis
  • Division of all the rest of cell parts but not
    equally (organelles)
  • Animals cell membrane pinches to form two cells
  • Plants new cell plate created between the two
    cells (becomes cell wall)

30
The Cell Cycle An Overview
  • 1)Interphase
  • 2)Mitosis
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • 3)Cytokinesis
  • Cell Division (Cell Reproduction) mitosis
    cytokinesis

31
Use an Acronym
  • For Mitosis
  • Prophase P
  • Metaphase M
  • Anaphase A
  • Telophase T
  • Make a sentence
  • Please Meet At Ten
  • Phil, Mary, And Tom

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Figure 11-2
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Links
  • http//en.wikipedia.org/wiki/TrisomyTrisomy
  • http//www.medgen.ubc.ca/wrobinson/mosaic/mos_how.
    htm

38
Mitosis Drawing
  • Fold a large sheet of paper in 3
  • You should have 3 columns on the front and 3 on
    the back
  • You will draw a cell in each stage of mitosis and
    include a written description of what is
    occurring at each stage
  • Stages Interphase, Prophase, Metaphase,
    Anaphase, Telophase, Cytokinesis
  • Notice that there are 6 stages and 6 coulmns on
    your sheet...1 stage per column!

39
Some facts
  • 500,000 deaths per year (more males)
  • Older age group stricken more often
  • More than 100 types of cancer, many due to
    mutations triggered by environmental factors
  • Highest cancer incidence male -
    prostate female - breast
  • Highest cancer deaths lung

40
Normal cells in culture
  • Organized structure
  • Limited cell growth
  • No overlapping

41
Cancer cells in culture
  • Disorganized
  • Overlapping structure
  • Uncontrolled cell growth

42
Some images to make this real look first at
normal skin
43
Cancerous Skin
44
What causes a normal cell to become a cancer cell?
45
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