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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 does a multi cellular organism require two types of cell division ?

There are two distinct type of cell divisions taking place in multicellular organisms. One is mitosis in somatic cells for growth and healing of wounds and the other is meiosis in reproductive cells for producing gametes having half the number of chromosomes in order to maintain the number of chromosomes in the organism. It is essential to maintain the characters of the species. Therefore both type of cell division are necessary for an organism. 

 


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

Crossing over.

Name an important event that occurs during meiosis and not during mitosis.

Crossing over takes place during meiosis but not during mitosis.

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. 

 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.

 Namethe five phases of of Prophase I.

The five phases of prophase 1 are
i. Leptotene
ii. Zygotene
iii. Pachytene
iv. Diplotene
v.  Diakinesis.