Download Genetics Cell Division

Genetics
Mitosis
Cell Theory Principle

“Where a cell exists, there must have been a
preexisting cell”
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“Omnis cellula e cellula”
(all cells come from cells)
Necessary Characteristic of Life: Cell
Reproduction

unicellular organism
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reproduces entire organism
multicellular
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growth
embryonic development
replacement of damaged or dead cells
Binary Fission
Reproduction in Bacteria
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genome (hereditary endowment)
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single, circular dsDNA
associated with proteins
single chromosome
replication averages minutes-3 hours
Steps of Binary
Fission
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chromosome replication begins, one
copy of the origin moves rapidly to
the other end
one copy of the origin is now at each
end of the cell; the cell elongates
replication finishes, the plasma
memebrane grows inward and a
new cell wall is formed
resulting in two daughter cells
Eukaryotes
vs.
larger cell size
greater quantity of DNA
histones
several chromosomes
Prokaryotes
smaller cell size
lesse quantity of DNA
other proteins
one chromosome
DNA Quantity in Eukaryotes

Amount of DNA has no direct relationship to
the complexity of that organism

ex.
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Alligators have more DNA than humans
frogs have more DNA than humans
DNA of Eukaryotes
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Chromosomes
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discrete entities
condensed DNA + protein
state found when DNA division occurs
Chromatin
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mass of DNA
loose coils of DNA + protein
state found when DNA replication occurs
Drawing of a Chromosome
short arms
centromere
kinetochore (protein)
sister chromatids
long arms
sister chromatids
www.biologycorner.com
Eukaryotic Chromosome

composition
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average human chromosome
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DNA = 40%
protein = 60%
5 cm (2.5cm = 1 in)
46 chromosomes in each cell

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2 meters of DNA
6 Billion base pairs
Karyotype

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particular array of chromosomes
chromosomes of one cell are arranged according
to:
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size
number
type information
extra or missing DNA
gender of individual
www.biotechnologyonline.gov.au/images/contentpages/karyotype.jpg
Human Cells

somatic cells = body cells
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46 chromosomes
diploid (2n)
gametes = sex cells (sperm, ova)
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23 chromosomes
haploid number (1n or n)
Homologous Chromosomes
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pair of chromosomes
one paternal, one maternal
Sister Chromatids
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identical
replicated forms of one chromosome
held together by one centromere
Chromosomes

Homologous (2)
 maternal, paternal

Replicated (2)
4 sister chromatids

http://www.phschool.com/science/biology_place/labbench/lab3/images/homologs.gif
Autosome vs. Sex Chromosome
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autosomal chromosomes
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22 pairs
sex chromosomes
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1 pair, XX or XY
Cell Cycle
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Interphase
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G1 phase
S
G2 phase
M (mitotic) phase
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mitosis (P, M, A, T)
cytokinesis
Interphase
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Preparing a cell for division
G1 phase (first gap)
growth of cell, enough cytosol for 2
S (synthesis)
DNA replication, DNA in chromatin
G2 phase (second gap)
chromosome condensation
microtubule synthesis
M Phase
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Mitosis (karyokinesis) - divide DNA, precise
division
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prophase (prometaphase)
metaphase
anaphase
telophase
Cytokinesis - divide the cytoplasm, rough
division
Mitosis
Prophase-Prometaphase
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Prophase
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DNA condenses
nucleoli disapear
sister chromatids
visible
spindle is forming
centrosomes migrate
Prometaphase
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nuclear envelope disapear
centromeres are at poles
condensation increases
kinetochore present
microtubules attach to kinetochore
Metaphase
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centrosomes convene
at the equator (plate)
kinetochores have both
microtubules from the
opposite poles attached
to each one
Anaphase
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proteins maintaining the
chromosomes attached
split
daughter chromosomes
move to the poles
cell elongates
Telophase
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2 daughter nuclei form
nuclear envelopes form
nucleolii reapear
chromosomes become
less condense
END of Mitosis
Cytokinesis
(division of cytoplasm)
Animals
microfilaments form contractile
ring and cell pinches in two
cleavage furrow
Plants
vesicles form plasma membrane, cell wall
material is deposited
cell plate
Cell Cycle Duration
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varies from 1-24 hours
example human liver cell
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Interphase:
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G1 phase…………......9 hrs.
S…………………..…10 hrs.
G2 phase……..………2 hrs
M phase: mitosis……50 min.
Cytokinesis……….....10 min
Controls of Cell Division
Cells in tissue culture do not divide if
1. essential nutrients are missing (growth factors)
2. poisons that inhibit protein (microtubules) synthesis
are present
3. cells are crowded
4. they cannot progress beyond the restriction point in
late G1
5. insufficient concentration of MPF (maturation
promoting factor, a complex of proteins)
6. they have reached maximum division (20-50x for
cells in culture)
Tumor
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mass of transformed cells
benign tumor
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cells remain at original site
lump can be completely removed
malignant tumor
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invasive cells
can impair functions of other organs
Cancer Cells
express abnormal cell division
1. density-dependent inhibition is absent
2. divide excessively, immortal
 HeLa cells 1951
3. can invade other tissues (metastasis)
4. genetically transformed
5. can form malignant tumors
6. can stop dividing at random points in
the cycle
normal cells

cancer cells
ACTIVITIES
what organism is
this tissue from?
E
name the stages A-E
which of these is not
an M stage?
B
C
F
where in the plant you
find this tissue?
what is "F"?
D
A

name the stage

what stage comes
before and after it?
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if this is a somatic
cell and n=10,
how many chromosomes
will it have?
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name the stage
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is it part of mitosis?
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give a visible characteristic.
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discribe what happens during
this stage
The End