Chapter 9, Problem 21A

Summary Introduction

Introduction:

Cells reproduce by a cycle of growing and dividing called the cell cycle. There are three main stages of a cell cycle; interphase, mitosis and cytokinesis. The given graph shows a cell over the course of its cell cycle.

  

Answer to Problem 21A

Correct answer :

The correct answer is option B. cytokinesis

Explanation of Solution

Explanation/justification for the correct answer:

Option B. cytokinesis−The part labeled Bshows cytokinesis. It is the stage in which a cell divides into two daughter cells. The cytoplasm divides resulting in genetically identical daughter cells. Each daughter cell receives half the number of DNA molecules. Hence this is the correct option.

Explanation for incorrect answer:

Option A. interphase−This is the first stage of cell cycle in which there is replication of DNA. As per the graph DNA molecules decrease from 8 to 4so there is division of DNA going on in part B. Hence, this is not the correct option.

Option C. mitosis- As per the graph DNA molecules decrease from 8 to 4 so there is division of DNA going on in part B. The cells are dividing into daughter cells with half the number of chromosomes passing to each daughter cell. Hence this is not the correct option.

Option D. metabolism−Metabolism is not a stage in cell cycle. It is a process of producing and utilizing energy. The area labeled B in the given graph shows cell division called cytokinesis.Hence this is not the correct option.