Biology: mitosis, a cell division process

1. Life sciences
(
Miss Cybil N. Khumalo
University of Johannesburg
201212375@student.uj.ac.za

2. CHROMOSOMES
 Chromosomes form when the chromatin network in the nucleus of
the cell, coil up, shortens and thickens.
 Each organism has a specific amount of chromosomes.
 All humans have 46 chromosomes.
 These chromosomes are arranged in identical pairs called
homologous chromosome pairs –
 Therefore humans have 23 homologous pairs of chromosomes.
 These chromosomes is only visible during cell division processes.
 One chromosome consist of 2 chromatids and one centromere
that attach the chromatids together.
 Each chromatid consist of genes which in turn consist of DNA.

3. CHROMOSOME
STRUCTURE
X and Y chromosomes:
gonosomes/sexchromosomes
Colored bands
represents
different genes

4. THE PHASES OF THE CELL CYCLE
The cell cycle includes the following phases:
 Interphase (include G1- , S- [DNA synthesis] and G2
phase)
 Mitosis
 Cytokinesis
 Growth
The result is 2 identical cells.

5. Why is Mitosis
important?
Allow an organism to
grow.
Repairs damaged
cells/tissue.
Replace dead cells/tissue.
Reproduction in some
simple organisms.

6. Where does Mitosis take place?
 In all somatic cells (include all body cells and
excludes the sex cells – sperm/egg cells)

7. The process of Mitosis.
 CONSIST OF A FEW PHASES:
 INTERPHASE
 PROPHASE
 METAPHASE
 ANAPHASE
 TELOPHASE

8. INTERPHASE
 Cell builds up enough energy for division
process.
 DNA replication occurs
 Cell look normal, like before division

9. PROPHASE
 Nuclear envelope and nucleolus
disappear.
 Chromatin become more tightly
coiled, and condenses into
individual chromosomes.
Chromosomes arrange randomly
in the cell.
 Centrioli move to opposite
poles, with spindle fibers
stretching between them.

10. METAPHASE
 The centrioli reached the opposite poles
with the spindle fibers in between.
 The chromosomes arrange randomly on
the equator, each single chromosome
attaching to a separate spindle fiber by
means of the centromere.

11. ANAPHASE
 The spindle fibers pull tight.
 The centromers attaching the
chromatids of the chromosomes split in
half.
 Daughter chromosomes move to
opposite poles.

12. EARLY TELOPHASE – KARYOKINESIS
(DIVISION OF NUCLEUS
 Daughter chromosomes reach poles.
 Nuclear envelope surrounds
chromosomes.
 Nucleolus reappear at each pole.
 Chromosomes become less condense
forming chromatin.
 Two identical nuclei has been formed

13. LATE TELOPHASE – CYTOKINESIS
(DIVISION OF THE CYTOPLASM)
 Invagination of the cytoplasm and plasma
membrane occurs. (Cleavage furrow forms in
animal cells and a cytoplasmic plate forms in
plant cells)
 Continues until the cell in divided into 2 separate
cells. (Identical to one another and to the original
cell)

14. MITOSIS PROCESS

15. CANCER
 Cancer is caused by the loss of cell cycle controls in
cancer cells.
 Cancer cells usually continue to divide well beyond a
single layer, forming a clump of overlapping cells called
a tumor.
 Malignant tumors invade surrounding tissues and can
metastasize exporting cancer cells to other parts of the
body, where they may form secondary tumors.
 They do not exhibit anchorage dependence or
density dependent inhibition.
(information from Campbell & Reece, Biology: 2010)

16. Ovarian cancer cells
Breast tumor
Ovarian cancer
cells dividing