Chapter 9, Problem 27A

Summary Introduction

To determine:

The average duration of mitosis.

Introduction:

The process in which a single cell divides into two identical daughter cells is termed as mitosis. In mitosis, parent cell and daughter cells are copy of each other. The main purpose of mitosis is to replace old cells and for growth.

Explanation of Solution

Given data:

Number of cells in interphase − 90

Number of cells in prophase − 13

Number of cells in metaphase − 12

Number of cells in anaphase − 3

Number of cells in telophase − 2

Total cells − 120

Time required by a cell to complete one cycle − 24 hours

Total number of cells in mitotic phase (M phase) = 13+12+3+2 = 30

The ratio of number of cells undergoing mitosis to total number of cells is termed as mitotic index.

$\begin{array}{c}\text{Mitotic index = }\frac{\text{Number of cells in mitotic phase}}{\text{Total number of cells}}\times 100\\ =\frac{30}{120}\times 100\\ =2.5\%\end{array}$

Time taken to complete one cell cycle = 24 hours

$\begin{array}{c}\text{Time taken in mitotic phase = 2}\text{.5\%}\times \text{24 hours}\\ \text{=}\frac{2.5}{100}\times 24\text{hours}\\ \text{=0}\text{.6 hours}\\ \text{=36 minutes}\end{array}$

So, the average duration of mitosis is 36 minutes.