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Saturday, 25 November 2017

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Biology: Mitosis vs Meiosis, definition and differences.



Mitosis and meiosis



Mitosis

This is the process by which cells increases in number and achieves growth. Mitosis occurs in five stages namely; Interphase, prophase, metaphase, anaphase and telophase. 

Mitosis occurs in somatic or body cell such as skin, bone marrow, lymph nodes and injured places as well as meristematic tissues in plant.

i) Interphase: In this phase,
  • chromosone becomes elongated and forms a network of fine thread called chromatid.
  • The nuclear membrane is nearly visible.
  • The nucleolus is also visible.



ii) Early prophase: In this phase,
  • Chromosone becomes visible as the chromatid thread condenses.
  • Chromosone are lone and thin.
  • The nucleolus starts to shrink.
  • There is a formation of spindle fibres.



    Late Prophase: In this phase,
  • chromosone becomes faster, thinner and very visible.
  • The nuclear membrane disappears.
  • The nucleolus disappears entirely.



iii) Metaphase: In this phase,
  • The chromosome arranges themselves along the equator.
  • The chromatids are attached to the spindle be the centromeres.



1v) Anaphase: In this phase,
  • The chromatids separate.
  • The chromatids start migrating to the poles.
  • The chromatids eventually get to the poles.



v) Telophase: In this phase,

  • The cell starts dividing into two.
  • The chromosone now loses their thick appearance.
  • The spindle structure disappears.
  • The daughter cells are formed.

Mitosis






Importance of mitosis

  1. It ensures that the diploid condition of the cell is retained from generation to generation.
  2. It helps in growth of multi-cellular organisms.
  3. It helps in asexual reproduction of animal and plant.
  4. Mitosis ensures that the exact copy of DNA (deoxyribose nucleic acid) are transmitted to daughter cell.




Meiosis

It is a two-successive cell division with my one duplication of chromosones. Meiosis is a reduction in cell division and the resulting in daughter cells. 

For example,
  • Ovules and pollen grains in plants.
  • Ovaries and testes in animals.


In animals, meiosis occurs in the formation of gametes sex cells such as eggs and spermatozoa. The process of gametes formation is called gametogenesis. The process involved in the production of spermatozoa by testes is called spermatogenesis, while the process of producing eggs by the ovaries is known as Oogenesis.


Importance of Meiosis

  • It aids formation of sperm in animals.
  • It aids formation of eggs or ova in female animals.
  • It aids the formation of pollen grains in flowering plants.
  • It aids the formation of ovules in flowering plants.






Differences between Mitosis and Meiosis

Mitosis
Meiosis
a) It occurs during the growth
of somatic cells and asexual
reproduction.
It occurs during
gamete’s production.                 
b) Two daughter cells or
off springs are formed
Four daughter cells or
off springs are formed.       
c) Chromosone number of
daughters and parent’s cells
are equal.                                         cells Is half the number
The chromosone
number of daughter cells
is half the number
in the parents’.

d) Off-springs produced by
mitosis is the exact replicate of the parents
Off-springs produced
by meiosis will show
Variation.
                                                                         











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