NCERT Class 11-Biology: Chapter –10 Cell Cycle and Cell Division Part 6

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Question 4:

Write brief note on the following

a. Synaptonemal complex

b. Metaphase plate

Answer:

a. Synaptonemal complex

Formed during Zygotene a sub stage of Prophase I.

Made up of protein, formed between two homologous chromosomes.

It contains a recombination nodule which consists of enzyme recombinase involved in crossing over.

b. Metaphase plate

It is an imaginary line, located in the centre of the cell.

Formed during metaphase.

The chromosomes gets attached to the spindle fibre and aligns themselves on the plate.

The movement of chromosomes toward the metaphasic plate is called congression.

Question 5:

Write briefly the significance of mitosis and meiosis in multicellular organism.

Answer:

Mitosis creates the cells necessary to add more mass to the body, as well as more cells to cope with the growth, such as new blood cells. In case of injury mitosis is involved in healing of the tissues.

Meiosis also produces genetic variation by way of the process of recombination.

It helps to conserve the no. of chromosomes in a species.

Question 6:

An organism has two pair of chromosomes (i.e., chromosome number = 4). Diagrammatically represent the chromosomal arrangement during different phases of meiosis-II.

Answer:

The following diagram shows different phases of meiosis –II of an organism which has two pairs of chromosomes.

Phases of meiosis

Phases of Meiosis

Phases of meiosis

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