Cell Cycle And Cell Division Class 11 Notes Biology Chapter 10 - CBSE

Chapter : 10

What Are Cell Cycle And Cell Division ?

Cell Cycle

Sequence of events by which cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells.

Phases of cell cycle

Interphase (G₁ phase + S phase + G₂ Phase)
M phase (Mitosis phases)
- Karyokinesis (division of nucleus)
- Cytokinesis (division of cytoplasm)

Mitosis

Mitosis is used to produce daughter cells that are genetically identical to the parent cells. The cell copies- or 'replicates' - its chromosomes, and then splits the copied chromosomes equally to make sure that each daughter cell has a full set.

Mitosis or indirect cell division

Karyokinesis
- Prophase
- Metaphase
- Anaphase
- Telophase
Cytokinesis

Significance of Mitosis

Growth-addition of cells.
Maintenance of surface/volume ratio. Maintain Nucleo-cytoplasmic ratio.
Maintains chromosomes number.
Regeneration.
Reproduction in unicellular organisms, lower plants and some insects.
Repair and wound heading.
Vegetative reproduction in plants takes place by mitosis.

Meiosis (Reductional Division)

Meiosis is a type of cell division that reduce the number of chromosome to half and results in the production of haploid daughter cells. It ensures the production of haploid phase in the life cycle of sexually reproducing organisms. It involves following events :

Two sequential cycles of nuclear and cell division called meiosis I and meiosis II but single cycle of DNA replication.
It involves pairing of homologous chromosome and recombination of them.
Four haploid cells are formed at the end of meiosis II.
Prophase I of Meiosis I is typically longer and involves five phases based on chromosomal behaviour, i.e., Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.

Meiosis or reduction division

Meiosis - I