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CELL DIVISION 1
MITOSIS
Hasimah Azit
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CELL DIVISION
FUNCTIONS IN:
Reproduction, Growth,
and Repair
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Core Concepts
All Organisms Consist of Cells and
Arise from Preexisting Cells
Mitosis is the process by which new cells aregenerated.
Meiosis is the process by which gametes are
generated for reproduction.
Unregulated Cell Division Can Lead toCancer
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Basic definitions
gene- basic unit of heredity; codes for aspecific trait
somatic cell- all body cells exceptreproductive cells
gamete- reproductive cells (i.e. sperm &eggs)
chromosome- elongate cellular structurecomposed of DNA and protein - they are thevehicles which carry DNA in cells
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diploid (2n)- cellular condition where each
chromosome type is represented by twohomologous chromosomes haploid (n)-
cellular condition where each chromosome
type is represented by only one chromosome
chromatid- one of two duplicated
chromosomes connected at the centromere
centromere- region of chromosome where
microtubules attach during mitosis andmeiosis
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Cell division involves
the distribution of identical geneticmaterial, DNA
to two daughters cells.
2n=46
2n=46
2n=46
two
identicaldaughter
cells
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Mitosis
The form of cell divisionby which a
somatic cell duplicates.
Mitosisis asexual reproduction.
Cell division is the continuation of lifebased on the reproduction of cells.
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The Cell Cycle
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Interphase
1. G1(gap) phase:
a. protein synthesis and metabolic activities.
b. most cell are arrested in this phase.
2. S phase:
a. DNA replication takes place.
3. G2(gap) phase:
a. Cellular growth and preparation for M phase.
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Cell Cycle
The dividingand non-dividingstages in the
life of a cell.
Phases:1. Interphase: growth and DNA replication
2. Prophase
3. Metaphase4. Anaphase
5. Telophase
Mitotic division
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Interphase
Comprises about 90%of the cell cycle.
Cellular growth:
a. protein synthesis
b. metabolic activities
c. DNAsynthesis
Made up of three phases:1. G1phase
2. S phase
3. G2
phase
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mitosis- nuclear/chemical events resulting
in two daughter nuclei which
have identical genetic material toeach other and to the mother cell
cytokinesis- division of the cytoplasm.
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Interphase
Nucleusand nucleolusvisible.
Nuclearmembrane
nucleolus
cell membrane
chromatin
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Question:
What is a chromosome?
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Answer:
A chromosomeis made up of a DNA-
histone protein complex called chromatin.
Chromatinis a long, thin fiber that is folded
and coiled to form chromosomes.
DNAdouble helix
Histone
proteins
chromosome
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Chromosomes
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Question:
What is a replicated chromosome?
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Answer:
A replicated chromosomeconsist of two
strands of identical chromosomal material
called chromatids(sister chromatids).
chromatid
chromatid
S phase: chromosomes replicate
chromosome
chromosome
centromere
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Question:
When is a chromatida chromatid?
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Answer:
A chromatidis a chromatidas long as it is
held in association with a sisterchromatidat
the centromere.
chromatid
chromatid
centromere
chromosome
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Mitotic Phase
Mitosis (karyokinesis)
a. nucleardivision of genetic material.
b. prophase-metaphase-anaphase-telophase
Cytokinesis
a. cytoplasmic division.
b. Indicator of telophase.
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Prophase
Centriolesmove apart (not found in plants).
Spindle fibers form and attach from
centriolesto centromeres by kinetochores.
Nuclear envelope fragments and disappears.
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Prophase
late prophaseearly prophase
centrioles
spindle fibers
centromere
nuclear envelope
disappearing
aster
fibers
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Question:
What attaches the spindle fibersto
the centromeres?
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Answer: Kinetochores
sister
chromatid
sister
chromatid
centromere
spindle fiber kinetochores
centriole
aster
fibers
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Metaphase
metaphase plate
centrioles
spindle fibers
aster
fibers
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Anaphase
Centromeresuncouple and spindle fibers
shorten.
Sister chromatids separate and move apart.
After separation, chromatidsare now
considered chromosomes.
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Anaphase
During this phase, the cell contains twice
the normal number of chromosomes.
Cell begins to elongate.
At the end, there are equal numbers of
chromosomesat the poles.
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Anaphase
No longer sister chromatids, now chromosomes
centriolesspindle fibers
aster
fibers
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Telophase
Cleavage furrowdevelops in animal cells
(Cytokinesisbegins).
Cell plate develops in plants(no cleavage
furrows in plants).
Nucleolus reappears.cell plate
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Telophase
Nuclear membrane reappears.
Chromosomesuncoil.
In the end, two genetically identical nuclei
(karyokinesiscompleted) are present.
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Telophase
cleavage furrow (cytokinesis)
nuclear membrane reformingnucleolus reappears
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Cytokinesis
Cytoplasmic division
Cell plate complete in plants
In the end, two separate daughter cells
produced with single nucleus.
cell plate
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Question:
A cell containing 20chromosomesat the
beginning of mitosis would, at its completion,
produce cells containing how manychromosomes each?
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Answer:
20 chromosomes
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Question:
A cell containing 40chromatidsat the
beginning of mitosis would, at its completion,
produce cells containing how manychromosomes each?
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Answer:
20 chromosomes