Question

What is cell cycle ? Explain how cell cycle times are determined

Answer 1

The cell cycle or cell-division cycle is the series of events that take place in a cell leading to its division and duplication of its DNA to produce two daughter cells.Two key classes of regulatory molecules, cyclins and cyclin-dependent kinases (CDKs), determinea cell's progress through the cell cycle.

Answer 2

Cell cycle
In the process of cell division daughter cells are produced by the division of parent cell . These daughter cells grow and again divide to form new daughter cells. Different stages of a cell , right from its formation to it's division constitute a cell cycle
Main parts of cell cycle are
1. Interphase: The materials required for cell division are synthesized during this step of cell cycle this is called preparatory stage of cell division it has been further divided into following phases
(a) First Growth Period or G1 phase - This phase takes 30-40% of total time taken by the cell cycle. During this phase a cell growth and synthesis necessary proteins and RNA required for the synthesis of DNA
(b) Synthetic Period or S phase - This phase takes 20-30% or total time taken in completion of cell cycle during this phase synthesis of DNA take place
(C) Second Growth Period or G2 phase - This phase takes 10-20% of total time taken by cell cycle . During this phase proteins required by the cell are synthesized
2. Division phase or mitotic Phase or M phase - This phase takes only 5-10% of total time taken by cell cycle. During this phase two nuclei are formed by the division of the nucleus of the cell . later on two daugher cells are produced due to division of the cytoplasm.

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