Tag: the origin of cells and cell division

• In mitosis, the number of chromosomes in the parent and progeny cells is the same. It is also known as equational division. 
• There is no crossing over taking place in mitotic cell division which leads to the formation of identical daughter cells.
  

• DNA duplication os required so that the genetic material in the cell is doubled and can be equally distributed between the 2 daughter cells. 
• On mitosis the DNA is duplicated during the S phase of the interphase after which the cell enters the cell division and the genetic material is distributed between the daughter cells equally. 
• In meiosis the cells undergoes meiosis 1 and meiosis 2 where the genetic material is already duplicated in the S phase of the interphase before entering the  cell division after the first meiosis the genetic material is halved of the mother cell. After this the cell enters the meiosis 2 where the stages are almost as same as the mitosis where the genetic material is distributed between the cells during the anaphase. 
• Therefore the answer option 'Meiosis I and mitosis' is correct. 

In a meiotic cell division, the different types of haploid cells produced will be 2$^n$, where n is the haploid chromosome number. In case, the diploid chromosome number is 12, the haploid chromosome number n will be 6. Thus different types of cells produced will be equal to 2$^6$ or 64 types.

Behaviour of homologous chromosomes is different in meiosis and mitosis. In meiosis the homologous chromosomes pair, exchange segments and then separate from each other. Exchange of segments between homologous chromosomes is called crossing over. In mitosis, homologous chromosomes do not pair and remain independent of each other.

if the number of bivalents is 8 in metaphase 1, then the number of chromosomes after meiosis -1 is 8 as the diploid stage of the cell persists.

In meiosis , synapsis (Pairing of homologous chromosome), Crossing over (exchange of chromosomal segment between nos sister chromatids) occurs which does not occur in mitosis.

The germ cells in gonads multiply by both mitotic and meiotic divisions. The germ cells proliferate mitotically before undergoing reduction division or meiosis. For example, in human males, the spermatogonia present on the inside wall of seminiferous tubules multiply by mitotic division and increase in numbers before undergoing meiosis.

• During mitosis, chromosome number remains the same and cells increase in number. Mitosis is the cell division in meristematic tissue. 
• Daughter cells produced after meiosis are haploid. Meiosis is the cell division that occurs in gametangia to produce gametes.

• Meiosis is the type of cell division in which homologous chromosomes separate after an exchange of fragments. As a result of meiosis, four haploid cells are produced which are all genetically different from each other. 
• This is due to the process of crossing over or exchange of segments between homologous chromosomes.

Meiosis occurs in two stages meiosis I and meiosis II. During meiosis I, homologous chromosomes separate and the number of chromosomes in daughter cells get reduced to half. This division is known as reductional division. During meiosis II, centromere splits and the chromosome number remains the same in the daughter cells. Hence, meiosis II is known as equational division. Hence, the number of chromatids in a chromosome at anaphase is 1 in mitosis and 2 in meiosis.