Chapter 11, Problem 8STP

Summary Introduction

Introduction:

The timing and rate of cell division are very important to the well- being of an organism. The rate of cell division varies depending on the type of cell. There is mechanism involving proteins and enzymes that control mitosis. A combination of these two substances is required to signal the cellular reproduction processes.

Answer to Problem 8STP

Correct answer :

The correct answer is option B. Cyclin builds up

Explanation of Solution

Explanation/justification for the correct answer:

Option B. Cyclin builds up−Cell cycle is controlled by a mechanism involving certain proteins and enzymes. Proteins called cyclins bind to enzymes called cyclin- dependent kinases (CDK) during the stages of interphase and mitosis to signal the cell to start the process of cell cycle. Different cyclin and CDK combinations control different activities at different stages of cell cycle. Hence, this is the correct option.

Explanation for incorrect answer:

Option A. Cells touch each other−Cyclinsbind to enzymes called cyclin- dependent kinases (CDK) during the stages of interphase and mitosis to signal the cell to start the process of cell cycle. Touching of cells do not trigger mitosis. Hence, this is not the correct option.

Option C. Environmental conditions are poor- Cyclinsbind to enzymes called cyclin- dependent kinases (CDK) during the stages of interphase and mitosis to signal the cell to start the process of cell cycle. Environmental conditions do not control cell cycle. Hence, this is not the correct option.

Option D. Growth factors are absent- Cyclinsbind to enzymes called cyclin- dependent kinases (CDK) during the stages of interphase and mitosis to signal the cell to start the process of cell cycle. Growth factors do not control mitosis. Hence, this is not the correct option.