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Cell Cycle and Cell Division

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CBSE Gujarat Board Haryana Board

## Previous Year Papers

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Class 10 Class 12
Describe the following

1. Synapsis
2. Bivalent
3. Chiasmata.

1. Synapsis: It occurs in zygotene stage. It is pairing of homologous chromosomes. It may be centric or random or preterminal.

2. Bivalent : A pair of homologous chromosomes is called bivalent.

3. Chiasmata : It is point in a tetrad where crossing over occurs.

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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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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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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 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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