Question

If a bacterial cell divides once every minute and takes 60 minutes to fill a cup, how much time will it take to fill half the cup?
(a) 30 min
(b) 32 min
(c) 29 min
(d) 59 min

Answer 1

Hint: Bacteria divide by the process of transverse binary fission. In this process, a single bacterial cell gets divided into two identical daughter cells which are clones of the parental cells i.e. same genetic makeup.

Complete Answer:
When a bacterial cell divides it gives rise to two new bacterial cells. If the life cycle of a bacteria is 1 minute, it means that the number of bacterial cells will divide every 60 seconds. So if it takes 60 minutes to fill a cup, it must take 59 minutes to fill half a cup as in 1 minute half cup full of bacteria will double to fill the cup completely.

Thus, it will take 59 minutes to fill half a cup with this bacteria.

Additional information: The life cycle of a normal cell is divided into:
Interphase: In this phase, the cell prepares for cell division and it includes the G1 phase, S phase, and G2 phase. In the S phase, replication of DNA takes place but chromosome number remains the same.
M Phase: This is the phase where actual cell division takes place including karyokinesis (the division of the nucleus) and cytokinesis (the division of the cytoplasm).
So, the correct option is ‘(d) 59 min’.

Note:
- A human cell divides once every 24 hours out of which $90\%$ of this time is occupied by interphase.
- Escherichia coli takes 20 minutes to give a new generation. Due to such a short life cycle, it is used in many scientific experiments such as Meselson and Stahl’s experiment.
- The life cycle of yeast (Saccharomyces cerevisiae) which is a unicellular fungus is about 90 minutes.