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PinkMonkey Online Study Guide-Biology

6.4 Comparison Between Mitosis and Meiosis

MITOSIS

MEIOSIS

1.

Occurs in somatic cells.

1.

Occurs in reproductive cells.

2.

Consists of only one nuclear division.

2.

Consists of two nuclear divisions M-I and M-II.

3.

Cytokinesis takes place only once.

3.

May take place only once (simultaneous type) or twice (successive type).

4.

Involves division of chromosomes.

4.

Involves separation of homologous chromosomes in M-I and division of chromosomes in M-II.

5.

Dividing cells can be haploid or diploid.

5.

Dividing cells are diploid.

6.

Does not involve either pairing of homologous chromosomes or crossing over.

6.

Pairing of homologous chromosomes and crossing over occur during Prophase-I.

7.

Two daughter cells are formed.

7.

Four daughter cells are formed.

8.

Number of chromosomes present in the mother cell is maintained in both the daughter cells. Therefore it is an equational division.

8.

Diploid number of chromosomes is reduced to haploid in each daughter cell. Therefore it is a reduction division.

9.

Original characters of the chromosomes are maintained in the daughter cells.

9.

Chromosomal characters are altered due to "crossing over" causing recombination of genes.

10.

Daughter cells are similar to each other and also to the original mother cell.

10.

Daughter cells differ from each other as well as from the original mother cell.

11.

Helps in growth and body repairs.

11.

Helps in the sexual reproduction and regulation of chromosome number in the life cycle of sexually reproducing organism.


SUMMARY : MEIOSIS

(i) Meiosis occurs in reproductive cells only. (ii) It occurs in diploid cells. (iii) The karyokinesis of meiosis consists of two complete nuclear divisions called first meiotic division (Meiosis-I or M-I) and second meiosis division (Meiosis-II or M-II). (iv) M-I is reduction division involving separation of homologous chromosomes. (v) M-II is equational division like mitosis which involves duplication of chromosomes. (vi) The four daughter nuclei are haploid due to the reduction division (M-I). Moreover, they differ from each other in the characters of chromosomes due to ’crossing over’ during Prophase-I of M-I. (vii) Cytokinesis may be successive or simultaneous dividing the diploid mother cell into four haploid daughter cells.


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Table of Contents

6.0 - Introduction
6.1 The Cell Cycle
6.2 Mitosis
6.3 Meiosis
6.4 Comparison between Mitosis & Meiosis

Chapter 7





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