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Cell Cycle and Cell Division

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Biology

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Biology

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Why is meiosis called the reductional division and mitosis called equational division?

Meiosis is called reductional division because number of chromosomes and amount of DNA in daughter cells is reduced to half than that of parent cell. In meiosis diploid number of chromosomes is reduced to haploid number.

Example. If a parent cell has 16 chromosomes then in daughter cells due to meiotic division number of chromosomes is reduced to eight.

Mitosis. It is called equational division because number of chromosomes and amount of DNA in daughter cells remain equal to parent cells.

Example. If a parent cell has 18 chromosomes, then in daughter cells formed by mitosis have each 18 chromosomes. 

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Name the process in which there is an exchange of genetic material between non-sister chromatids of homologous chromsomes during meiosis.

Crossing over.
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What is polyteny ?

Polytene chromosomes are giant chromosomes which are formed due to repeated DNA replication without cell division. They are found in some insects. 
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 What are two types of cells on the basis of presence or absence of nucleus ?

On the basis of the presence and absence of nucleus the cells are divided into two types Eukaryotic and prokaryotic cells.
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 Namethe five phases of of Prophase I.

The five phases of prophase 1 are
i. Leptotene
ii. Zygotene
iii. Pachytene
iv. Diplotene
v.  Diakinesis. 
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Name an important event that occurs during meiosis and not during mitosis.

Crossing over takes place during meiosis but not during mitosis.
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