Question

6. What is meant by the concept that cells go through a cell cycle?

7. List the phases of the cell cycle with a brief description of what occurs in each phase.

8. Label the stages and key features of each stage of mitosis.

9. What is the role mitotic spindle? What is it made of?

Answer 1

Answer 6- Cell cycle is also known as cell division cycle which is a series of events that occurs in a cell and that lead to DNA duplication and cytoplasm division and to produce into two daughter cells. hence the concept behind this refers to the life cycle of a cell which comprises all the steps from when cells is formed upto when cell divides.

Answer 7- These are the following phases of cell cycle :

a) Interphase (G1, S and G2) : During this phase, all the cellular organelles get doubled in number, DNA replication occurs and all the protein required for further process get synthesized in this phase.

b) Mitotic Phase (Mitosis and Cytokinesis): During this phase cell divides its DNA and cytoplasm to make new daughter cells.

c) G₀ phase : During this phase those cells which does not divide rapidly or or have not to divide further, they go into the resting phase or exit phase known as G_o phase.

Answer 8- Mitosis stages are as follows :

a) Prophase : In this stage chromatin get condensed, nuclear envelope get break down and spindle formation occurs at two opposite poles.

b) Metaphase :In this stage, spindle get matured and all the chromosome get aligned at the metaphase plate (an equator plane that is equally distant from both the pole. During this, nuclear membrane get disappeared.Chromosomes are aligned at the metaphase plate with equal force of polar fibres that is pushing on the centromere of the chromosomes.

c) Anaphase: In this stage, paired chromosome or can say sister chromatids get separate and move to opposite end of the cell. Spindle fibres which are not connected to the chromatids are lenghten and they help in elongation of the cell. during end of this phase, each pole have complete chromosome.

d) Telophase : At this stage, chromosome get separated into new nuclei in the two new daughter cells. This is followed by the cytokinesis in which cell cytoplasm divided into the two new emerging daughter cells. Nuclear membrane get reformed and chromosome get unwind into chromatin.

Answer 9- These mitotic spindle are made up of microtubules and some associated proteins which help in segregation of chromosomes into new daughter cells during mitosis process.