A population of T cells was stimulated to proliferate in response to a particular antigen. A sample of 1000 stimulated cells was analyzed for total DNA content. Of the 1000 cells, 400 had a 2n amount of DNA, 200 had a 4n amount of DNA, 200 cells had between a 2n and 4n amount of DNA. Additional analysis revealed that 200 of the cells were in various stages of M phase and that M phase lasted 2 hours. What is the total length of the cell cycle?

21. 2 hours.

Explanation:

The cell cycle of an organism is divided into the the G1 (gap 1) phase, S phase (synthesis phase), G2 phase (gap 2) and mitotic phase.

The length of the cell cycle can be calculated by the following formula;

length of the cell cycle = Total number of cell * time to divide a cell/1000.

Here, time to divide a cell is 24 hours. (Human cells as a reference)

400 had a 2n amount of DNA.

length of the cell cycle = 400 * 24/1000

=9.6 hours.

200 had a 4n amount of DNA

length of the cell cycle = 200 * 24/1000

=4.8 hours.

200 cells had between a 2n and 4n amount of DNA.

length of the cell cycle = 200 * 24/1000

=4.8 hours.

The cells of M phase requires 2 hours.

Total length of the cell cycle = 9.6+4.8+4.8+2 hours

Total length of the cell cycle = 21.2 hours.

Thus, the answer is 21.2 hours (if treating the cell as human cell).