Notes, Exercises, Videos, Tests and Things to Remember on Introduction to Cell Division
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The process of dividing the preexisting cell into two or more daughter cells is called cell division.
The process of cell division in which a diploid mother cell will divide into two identical daughter cells is called mitosis cell division. In this division, thenumber of chromosome in mother cell and daughter cells is same.
The process of cell division in which a diploid mother cell will divide into four haploid daughter cells is called meiosis cell division. In this division, the chromosome number is reduced to half in the daughter cells.
|Mitosis cell division||Meiosis cell division|
|One diploid mother cell divides into two diploid daughter cells||One diploid mother cell divides into four haploid daughter cells.|
|It is an equational cell division.||It is a reductional cell division.|
|It generally occurs in somatic cells.||It only occurs in reproductive cells.|
|It helps for physical growth.||It supports reproduction.|
|This type of division starts immediately after formation of zygote.||This type of cell division starts only after an individual becomes sexually mature.|
|It is a form of asexual reproduction.||It is a form of sexual reproduction.|
The amitosis (also called direct cell division) is the means of asexual reproduction in acellular organisms like bacteria and protozoans and also a method of multiplication or growth in foetal membranes of some vertebrates. In amitosis type of cell division, the splitting of a nucleus is followed by cytoplasmic constriction.
During amitosis, the nucleus elongates first and then assumes dumbbell- shaped appearance. The depression or constriction increases in size and ultimately divides the nucleus into two nuclei; the division of nucleus is followed by the constriction of cytoplasm which divides the cell into two equal or approximately similar halves.
Therefore, without the occurrence of any nuclear event, two daughter cells are formed.
Mitotic cell division
Meiotic cell division
i. It takes place in all somatic cells.
ii. One mother cell produces two daughter cells.
iii. Daughter cells are identical to each other and to the mother cell.
iv. The daughter cells are diploid (2n)
v. The daughter cells can survive independently.
i. It takes place in germinal cells.
ii. One mother cell produces four daughter cells.
iii. Due to crossing over daughter cells vary among each other.
iv. The daughter cells are haploid (n).
v. The daughter cells cannot survive independently.
Anaphase of mitosis
Anaphase of meiosis
i. The chromatids are separated and move towards the opposite poles after the division of centromere.
ii. Chromosomes are similar.
i. The chromatids move towards the opposite poles without the division of centromere.
ii. Chromosomes are dissimilar.
The formation of two or four daughter cells from a parent cell is called cell division. During the cell division, each daughter cell gets equal or half number of chromosomes. The two types of cell division are mitosis and meiosis.
The number of chromosomes in the cells produced after meiosis I is half of that in mother cell. Due to its reduction in chromosome number, meiosis I is called reduction divisions. As the number of chromosomes in daughter cell remains the same as in the immediate mother cell due to meiosis II, it is called equational division.
Plant cells have cell wall that gives rigid shape to them. During cytokinesis a cell plant is formed at the equatorial region of the cell due to the deposition of cell wall materials. This cell plate is transformed to cell wall dividing the mother cell into two/ four daughter cells. As animal cells lack cell wall, they are flexible. During cytokinesis, furrows are formed at the equatorial region. When the furrows deepen, the cell divides into two/four daughter cells.
Cell division is necessary for organisms because: a. Cell division helps in growth and development of each organ and ultimately the whole organism. b. It helps in replacing the dead and damaged cells of the body. c. It helps in asexual reproduction when the traits of parents are conserved in offspring. d. It brings variation among individuals of a population. e. It helps in inheritance from parents to offspring.
The division of nucleus is called Karyokineis while the division of cytoplasm is called cytokinesis.
Chromatin is the entangles mass of chromosomes where individual chromosomes are not distinguished. Chromatid, on the other hand, is the product of replication of chromosomes. Each chromosome bears two chromatids. Chromatin exists in Interphase and Telophase while Chromatids exists in Prophase, metaphase and anaphase.
At the end of telophase of mitosis two nuclei and meiosis four nuclei is formed.
Which one is reductional cell division?
Meiosis cell division
Mitosis cell division
None of Above
Equational cell division
Which one helps for physical growth?