A student examines a thin section of an onion-root tip and records the number of cells that are in each stage of the cell cycle. She observes 93 cells in interphase, 15 cells in prophase, 4 cells in metaphase 6 cells in anaphase and 2 cells in telophase. If the complete cell cycle in an onion-root tip cell requires 24 hours, what is the average duration of each stage in cycle?

given:

Total number of cells in all stages = 93+15+4+6+2 = 120

Total time = 24 hours.

solution:

Percentage of cells in interphase

= 93 * 100 / 120 = 77.5%

 in prophase

=15 * 100 / 120 = 12.5%

 in metaphase

= 4 * 100 / 120 = 3.33%

 in Anaphase

= 6 * 100 / 120 = 5%

 in telophase

= 2 * 100 / 120 = 1.66%

The percentage of cells present in various phases exhibits the time spend by each cell in that phase.

Total minutes

= 24*60 = 1440

Total minutes spent in interphase

= 77.5 * 1440

= 1116 minutes

in prophase =12.5 *1440

=  180 minutes

 in metaphase = 3.33*1440

=  48 minutes

in Anaphase = 5*1440

= 72 minutes

 in telophase = 1.66*1440

=  24 minutes

b. the carbon cycle ensures living things have a source of hydrogen