Question

Please only answer in sentences

1) Describe cell cycle and age-dependent changes in the cell cycle.

Answer 1

Answer - The cell cycle has 4 stages consisting of Gap 1 (G1), Synthesis, Gap 2 (G2) and mitosis. An active cell will undergo these steps as it grows and divides.

After completing the cycle, the cell either starts the process again from G1 or exits the cycle through G0. In G0, the cell undergo terminal differentiation.

The stages in the cell cycle include G1, S and G2, together called interphase.

1) G1 phase- In this phase, Cell increases in size and Cellular contents gets duplicated.

2)S phase- Here, the DNA replication takes place and each of the 46 chromosomes (23 pairs) is replicated by the cell.

3)G2 phase- During this phase cell grows more and it's organelles and proteins develop in preparation for cell division.

4)M phase-Mitosis followed by cytokinesis. Resulting in formation of two identical daughter cells

5)G0 phase- It is a resting phase.It is a permanent state for some cells, while others may re-start division if they get the right signals.

Age-dependent changes -

In normal aging of a diploid cell where it loses its ability to divide.

Sometimes it is suggested that senescence occurs as a result of programmed gene expression changes, or due to an accumulation of DNA double strand breaks or toxins.

Cellular senescence isdetected by the activity of senescence Associated ß-galactosidase (SA-ß-gal), a hydrolase enzyme that catalyzes the hydrolysis of ß-galactosidase into monosaccharides only in senescent cells.

Programmed cell death happens naturally by cascade of signals within the cell itself. The programmed cell death that is apoptosis, plays an important role in population control and prevents massive cell growth which could lead to a possible tumor.