please explain meiosis and mitosis with proper elaborations and if possible with the help of videos.. please its very important..
Mitosis is the mode of cell multiplication which occurs to increase the number of cells with no change in chromosome number or ploidy of the cell. It occurs in all the SOMATIC CELLS (cells of body not involved in sexual reproduction) for their growth and repair and also in gametes in initial stages to increase their number.
Meiosis is a reductional division which occurs in gametes i.e. cells involved in sexual reproduction. It occurs during the formation of gametes to make the cells haploid (n) i.e. the number of chromosomes becomes half before fertilization so that the number of chromosomes and ploidy of the organism is retained in the zygote.
Mitosis | Meiosis | ||
(i) | It involves single division, resulting in the formation of two daughter cells. | (i) | It involves two successive divisions, namely meiosis I and II, resulting in the formation of four daughter cells. |
(ii) | It is also known as equational division as the daughter cell has the same number of chromosomes as the parent cell. | (ii) | Meiosis I is known as reductional division where the chromosome number is reduced to half. Meiosis II is known as equational division where the sister chromatids separate while the chromosome number remains the same. |
(iii) | The prophase stage is short and does not comprise of synapsis, crossing over, and the formation of chiasmata. | (iii) | Prophase I stage is very long. It comprises of five stages. In the zygotene stage of meiosis I, the pairing of homologous chromosomes takes place. During the pachytene stage, crossing over occurs while in the diplotene stage, chiasmata formation occurs. |
(iv) | It plays a significant role in cell growth, repair, and healing of wounds. | (iv) | It brings about variation and maintains constant chromosome number from one generation to another. |
(v) | It mainly takes place in the somatic cells. | (v) | It mainly takes place in the reproductive cells. |