Chapter 9, Problem 30A

Summary Introduction

To replace:

The incorrect term with correct vocabulary terminthe given sentence.

Introduction:

Cancer occurs when the normal cell cycle is disrupted and the cell does not respond to control mechanisms. Cancer is uncontrolled growth and division of cells. These unchecked cancer cells can even kill the organism by crowding out normal cells. The changes occur in regulation of cell growth and division of cancer cells due to mutations or changes in certain segments of DNA.

Answer to Problem 30A

Carcinogens are substances that cause cancer.

Explanation of Solution

Various environmental factors can affect the occurrence of cancer cells. Substances and agents that are known to cause cancer are called carcinogens. Some common carcinogens are asbestos, cadmium, benzene, tobacco, ultraviolet radiation, X- rays, etc. Not all cancers can be prevented but avoiding known carcinogen can help reduce the risk of cancer.

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 start the process of cell cycle. Different cyclin and CDK combinations control different activities at different stages of cell cycle. Cyclins do not cause cancer.

Hence the correct word in the given sentence is carcinogen and not cyclin.