Question

Define cell cycle. Describe various phases of cell cycle. Add a note on significance of mitotic cell division

Answer 1

Here is your answer :

Cell cycle is a series of events that take place in a cell leading to the duplication of its DNA and the subsequent division of the cell to produce two daughter cells.

A cell cycle consists of two phases:

(i) a non dividing phase called the interphase

(ii) a dividing phase called M - phase or simply mitosis

INTERPHASE :

The two daughter cells produced from a mother cell are relatively small with a full sized nucleus but relatively little cytoplasm.These cells are said to be in interphase.During this phase , they prepare for the next cell division and grow to the same size and as their mother cell .

Interphase has three phases :

(i)First Growth Phase or G1 phase -

RNA and proteins are synthesised , the volume of cytoplasm increases . Mitochondria ( in animals ) and chloroplast ( in plants ) divides as tgey contain their own DNA.

(ii) Synthesis Phase or S phase -

More DNA is synthesised , the chromosomes are duplicated.

(iii)Second Growth Phase or G2 phase -

This is a shorter growth phase , in which RNA and proteins necessary for cell division continue to be synthesised .

MITOSIS :

Mitosis is the cell division in which one parent cell divides into two identical daughter cells. Mitosis occurs in somatic ( body ) cells and occurs throughout life.

Significance of mitosis :

The most important aspect of mitosis is that the same normal chromosome number is maintained at each cell division. In a mitiotic division full set of chromosomes is passed on each daughter cell . That is diploid 2n number of chromosomes. In humans 46 chromosome or 23 pairs of chromosomes are passed to two identical daughter cells.

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Answer 2

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During the mitotic (M) phase, the cell divides its copied DNA and cytoplasm to make two new cells. M phase involves two distinct division-related processes: mitosis and cytokinesis. ... Mitosis takes place in four stages: prophase (sometimes divided into early prophase and prometaphase), metaphase, anaphase, and telophase.