Question

Cell cycle: Explain the function of mitosis. What major events occur during each of the four phases of the cell cycle (G1, S, G2, M)? What is interphase? What is G0 and what types of cells enter G0? How can a cell’s stage in the cell cycle be identified experimentally? Describe the structural changes that occur as a cell proceeds through M phase. In particular, how do centrosomes, microtubules, the nuclear lamina and envelope, chromatin and chromosomes, centromeres and kinetochores, plasma membrane and actin filaments behave and function to bring about the separation of one cell into two? How are these events conventionally divided into stages (prophase, prometaphase, metaphase, anaphase and telophase)?

Answer 1

q. Explain the function of mitosis.

ans. Mitosis is a type of cell division which has very important functions such as-

• It increases the number of cells and causes growth.
• Damages and repairs the tissues.
• Asexual reproduction in some unicellular animals such as amoeba.
• Vegetative reproduction in plants.
• In meiosis, the first stage involves mitosis for example in gametogenesis such as oogenesis and spermatogenesis.

q.What major events occur during each of the four phases of the cell cycle (G1, S, G2, M)

ans. G1- cell growth phase

S- DNA synthesis phase

G2 - growth and preparation phase for mitosis

M- Mitotic phase

q. What is interphase?

ans. It is the stage of the cell cycle where a cell prepares itself to divide or duplicate. It includes G1, S and G2 phases. In this phase, chromosomes are not visible and the nuclear membrane is intact.

q. What is G0 and what types of cells enter G0?

ans.Many adult cells can enter a non-dividing phase called as G0 phase. It can last up to a few days or the whole life of an organism. For example, liver cells can stay in this phase for a year or so. Thus it is a quiescent stage. Usually differentiated cells enter the G0 phase such as neuronal cells.