Question

Use the data provided below to determine the average length of each stage of the cell cycle. Try to explain the discrepancies in the raw data between the groups. How do the results compare to what is stated in the literature?

Data for the last question on the Mitosis Lab

                   % Interphase % Pro %Meta. % Ana. % Telo.   Total Cells counted

Group One     76.2%         14.6%      4.0%    3.3%       1.9%      808

Group Two      55%          34%           4%      4%         4%          578

Group Three    52.5%        34.5%       3%       6%         4%         537

Group Four       81%          5%            2%       5%         7%         490

Group Five        75%         16%          3%       3.5%       2.5%      878

Answer 1

A) Duration/length of cell cycle (minutes) = (number of cells in the stage / total number of cells ) * cell cycle duration

as in the question there is nothing mentioned about the type of cell (whether it is yeast cell or any other eukaryotic cell) so, without given cell cycle duration the length of each stage cannot be calculated.

but, for example - let the cell cycle duration be = 24 hours = 1440 minutes

group 1- % interphase = 76.2% , total cell counted for group 1 = 808 cells

no. cells in interphase = 0.762* 808 =  615.69 = approx. 616 cells in interphase

length of interphase (minutes) = 616/ 808 *1440 = 1097.82 minutes = approx. 1098 minutes (18.3 hours)

2) The discrepancies in the raw data between groups is due to asynchronous growth of cells. Here, the number of cells studied by each group is different. Cell-cycle is a strict and highly controlled process, in which there are checkpoints at every cell cycle stage. These checkpoints assure that only those cells that have attained a proper size in G1 phase (Interphase) should be allowed to proceed to next stage of cell cycle. so small cells, that have not attain proper size (above a given threshold size limit) are not allowed to proceed to next stage until they first attain the maximum size. hence, larger cells (cells that have attain max. size after duplication in G1 phase) move faster to different cell cycle stages and undergo faster cell division than smaller sized cells. This creates asynchronous growth pattern between the cells. This is one of the many reasons why some cells divide faster than other.

3) According to literature, Out of the 4 stages of cell cycle, interphase (G1) requires the maximum time of overall time required for cell cycle. This is becasue, the cell prepares itself to undergo cell division (only in favourable conditions). Most of the cells undergoing cell division requires much more time to grow and double their intracellular content (mass of proteins), their cellular organelles in comparison to DNA synthesis (DNA replication). In accordance to the result for above data (after calculation ?), the interphase stage should have the highest average length incomparison to other stages, so max. number of cells in interphase are preparing themselves to divide by doubling their intracellular content.