Question

1. Part A) If a random sample of cells from one of your organs such as your liver or kidneys were checked under a microscope, doctors would expect to see ALL the cells in interphase. If a measurable number of cells were in mitosis, that would be a sign that you might have cancer or be close to developing cancer. Explain why the cells in your functioning organs SHOULD all be in INTERPHASE, not in mitosis. Hint: Make sure to mention "checkpoints" and "cell cycle" in your explanation! Part B) What are the primary cellular activities occurring during interphase other than the activities a cell might do if it were preparing for mitosis?

Answer 1

A) some cells in adult animals do not appear to exhibit division (e.g.,heart cells, nerve cells etc.) and many other cells divide occasionally, as needed to replace cells that have been lost because of injury or cell death.

In animals, mitotic cell division is only seen in the diploid somatic cells.

Functioning organ cells do not divide and enter an inactive stage called quiescent stage of cell cycle.

Thus division in them show sign of cancer as cancer is uncontrolled division of cells.

B) Interphase (also called as resting phase) is the time during which cell is preparing for division. It lasts more than 95% of the duration of cell cycle. During interphase cell growth and DNA replication occur in an orderly manner.

Interphase is divided into three phases :

1. Gap 1 phase : RNA, proteins, nucleotides, amino acid and energy rich compounds are synthesised.

2. S (Synthesis) phase : In animal cells, DNA replication occurs in nucleus, centriole duplicates in the cytoplasm. Amount of DNA per cell doubles.

3. Gap 2 phase : proteins are synthesised in preparation for mitosis while cell growth continues.