Post on 15-Jul-2015
Edited by: Hasimah Azit
CELL DIVISION FUNCTIONS IS to:
Produce new cells for: reproduction – gamete growth – new cells and repair – replace dead
cells
Basic definitions
gene - basic unit of heredity; codes for a specific trait
somatic cell - all body cells except reproductive cells
gamete - reproductive cells (i.e. sperm & eggs) chromosome - elongate cellular structure
composed of DNA and protein
diploid (2n) - cellular condition where each chromosome type is represented by two homologous 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 and meiosis
Basic definitions
Cell division involves
the distribution of identical genetic material, DNA
to two daughter’s cells.
2n
2n
2n
twoidenticaldaughtercells
The Cell Cycle
Cell CycleCell Cycle
The dividingdividing and non-dividingnon-dividing stages in the life of a cell.
Phases:
1.1. InterphaseInterphase: growth and DNA replication
2.2. ProphaseProphase
3.3. MetaphaseMetaphase
4.4. AnaphaseAnaphase
5.5. TelophaseTelophase
6. Cytokinesis – 6. Cytokinesis – cytoplasm dividedcytoplasm divided
Mitotic divisionMitotic division
InterphaseInterphase
1. 1. GG11 (gap) phase: (gap) phase:
a. grow into matured size and protein is synthesizedb. most cell are arrested in this phasemost cell are arrested in this phase.
2. 2. S phase:S phase:a. DNA replication DNA replication takes place.
3. 3. GG22 (gap) phase: (gap) phase:
a. Cellular growth and energy and organelles preparation for M phaseM phase.
MitosisMitosis
The form of cell divisioncell division by which a somatic somatic cell cell duplicates.
MitosisMitosis is asexual reproduction.asexual reproduction.
Cell division Cell division is the continuation of life based on the reproduction of cells.
mitosis - nuclear/chemical events resulting in two daughter nuclei which have identical genetic material to each other and to the mother cell
cytokinesis - division of the cytoplasm.
Mitosis division Mitosis division
Look at the section through the tip of an onion root tip and try to recognize:
* dividing cells – mitotic cells
* elongated cells
Onion root tip
Mitotic cellsElongated cells
InterphaseInterphase
NucleusNucleus and nucleolusnucleolus visible.
Nuclear membrane
nucleolus
cell membrane
chromatin
A chromosomechromosome is made up of a DNADNA
ChromatinChromatin is a long, thin fiber that is folded and coiled (invisible).
chromosome
Duplication of chromosome – from single strand to double strand
Chromosome replicationChromosome replication
A replicated chromosomechromosome consist of two strands of identical chromosomal material called chromatidschromatids (sister chromatidssister chromatids).
chromatid
chromatid
S phase: chromosomes replicate
chromosome
chromosome
centromere
A chromatidchromatid is a chromatidchromatid as long as it is held in association with a sistersister chromatidchromatid at the centromerecentromere.
chromatid
chromatid
centromere
chromosome
ChromatidChromatid
ProphaseProphase
Longest phaseLongest phase
Nucleolus disappears
Chromatin material condenses into chromosomeschromosomes, consisting of two sister chromatidssister chromatids.
ProphaseProphase
CentriolesCentrioles move apart (not found in plants).
Spindle fibers Spindle fibers form and attach from centriolescentrioles to centromeres centromeres
Nuclear envelope fragments and disappears.
ProphaseProphase
late prophaselate prophaseearly prophaseearly prophase
centrioles
spindle fibers
centromere
nuclear envelopedisappearing
asterfibers
Find the stages in the picture below
MetaphaseMetaphase
Shortest phase
CentriolesCentrioles are at opposite ends of the cell and attached with aster fibersaster fibers.
ChromosomesChromosomes move to the metaphase platemetaphase plate (equatorial plateequatorial plate - center of cell).
MetaphaseMetaphase
metaphase plate
centrioles
spindle fibers
asterfibers
AnaphaseAnaphase
CentromeresCentromeres uncouple and spindle fibers spindle fibers shorten.
Sister chromatids Sister chromatids separate and move apart.
After separation, chromatidschromatids are now considered chromosomeschromosomes.
AnaphaseAnaphase
During this phase, the cell contains twice the normal number of chromosomeschromosomes.
Cell begins to elongateelongate.
At the end, there are equal numbers of chromosomeschromosomes at the poles.
AnaphaseAnaphase
No longer sister chromatidssister chromatids, now chromosomeschromosomes
centriolesspindle fibers
asterfibers
TelophaseTelophase
Cleavage furrowfurrow develops in animal cells (CytokinesisCytokinesis begins).
Cell plate Cell plate develops in plantsplants (no cleavage furrows in plants).
Nucleolus reappears.
cell plate
TelophaseTelophase
Nuclear membrane reappears.
ChromosomesChromosomes uncoil.
In the end, two genetically identical nuclei (karyokinesiskaryokinesis completed) are present.
TelophaseTelophase
cleavage furrow (cytokinesis)
nuclear membrane reforming nucleolus reappears
CytokinesisCytokinesis
Cytoplasmic divisionCytoplasmic division
Cell plate Cell plate complete in plantsplants
In the end, two separate daughter cells produced with single nucleus.
cell plate
Question:Question:
A cell containing 2020 chromosomeschromosomes at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes eachchromosomes each?
Answer:Answer:
20 chromosomes20 chromosomes
Question:Question:
A cell containing 4040 chromatidschromatids at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes eachchromosomes each?
Answer:Answer:
20 chromosomes20 chromosomes
What is cancer?
A cancer cell is a cell that grows out of control.
Unlike normal cells, cancer cells ignore signals to stop dividing, to specialize, or to die and be shed.
Growing in an uncontrollable manner and unable to recognize its own natural boundary, the cancer cells may spread to areas of the body where they do not belong.
White blood cells attack the cancerous cell!
Find your self:
How the cancerous cells look like?
How these cells affect the health?
How these cells spread? What causes the cancer in
human?
Website for you to visit:
http://www.cellsalive.com/mitosis.htm http://www.biology.arizona.edu/Cell_bio/tuto
rials/cell_cycle/cells 3.html http://www.accessexcellence.org/RC/VL/GG/
mitosis.php
http://training.seer.cancer.gov/module_cancer_disease/unit2_whatscancer3_cell_biology.html