Thank us later but you didn't learn this about cell cycle !

Other than practicing previous entrance papers, you should take a look to the type of questions also which are parts of that paper. Why I am suggesting this? Well! Yes you can have certain questions from the topic that I am going to discuss here.

The topic is cell cycle & the steps involved in it. You need to learn each & every line very carefully as its really very important.

In cell division, basically copying of all cellular material & then cleavage of that material (with cell) occurs. This whole story of division is covered under cell cycle. Didn’t get me? Ok! During the process of cell division externally, process of cell cycle also goes on.

This story of cell cycle occurs in 4 phase’s viz. G1, S, G2 & M phase.

G1, S & G2 phase comes under interphase. M phase is basically mitosis phase (Fig A). Copying of required cellular components occur during interphase. Complete cell division occurs during M phase.  In simple words, you may say that interphase is a kind of check point which decides whether a cell can move into M phase or not. M phase is also divided into sub parts.

Cell cycle is a continuous process.

Let’s talk about interphase first.

G1 phase

G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components, such as the centrosomes undergo replication. Before cell begins DNA replication, it must ensure that it is biologically ready to take on such a process. G1 is the phase when this cellular monitoring takes place.

Conditions are made suitable for DNA synthesis in this phase. In case cell is not ready to undergo DNA synthesis, it enters into one more phase which is G0 phase. Once cell is in appropriate condition to undergo DNA synthesis, it enters into next phase i.e. S phase. Cell can enter into S phase either from G1 phase or G0 phase. G0 phase can past for days, weeks or even years.

S phase

It is basically the synthetic phase. DNA which is packaged into chromosome is replicated. In simple words, genetic material is doubled with identical gene setup. Doubled chromosome now enters into G2 phase.

G2 phase

This phase of interphase is basically present between the end of DNA replication & just before the starting of cell division. It is considered as a safety gap or check point to ensure the duplication of entire genetic material & all the organelle of the cell.

You may also call G2 phase as a final chance of it to grow before its division & forming two independent bodies.

M Phase –

This phase causes cell division & it lasts for about one hour.  The replicated chromosome align themselves to ‘mitotic apparatus’ & here sister chromatids get separated from each other. Initially this step involves division of nucleus (Karyokinesis) & then division of cytoplasm (Cytokinesis).

This phase is a continuous process & involves 5 stages. Viz. Prophase, prometaphase, metaphase, anaphase & telophase.

Take a look to this picture. Give your few minutes as every step is clearly defined in this picture.

For more information on cell cycle & cell division, please refer to the link.

In case if you have any query, please post it over here. Your all queries will be answered as soon as possible.

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