Chapter 21, Problem 1TY

Summary Introduction

Introduction: Genome is defined as the complete genetic material that is present in an organism. It consists of the coding as well as the non-coding parts of DNA. The study of the genome is termed as genomics. Restriction enzymes are widely used enzymes in the field of genomics. These enzymes were discovered by Werner Arber, Hamilton Smith, and Daniel Nathans.

Answer to Problem 1TY

Correct answer: The restriction enzymes are used in gene cloning experiments and they are used to cut DNA into pieces. These enzymes are used by the bacteria to avoid viral infections. Restriction enzymes produce sticky-ends at the terminal ends of DNA fragments. Hence, the correct answer is option d.

Explanation of Solution

Reason for correct answer:

Restriction enzymes were discovered around 1960. They are used in gene cloning experiments to cleave the DNA into small fragments. This enzyme is highly specific in nature. It cuts the DNA at only particular sites known as the restriction sites. This enzyme produces sticky ends at the terminal ends of the DNA. Moreover, it has been observed that microorganisms produce restriction enzymes naturally as a part of their defense mechanism. For example, a bacterial cell produces these enzymes to prevent the invasion of any viral infection.

Option d. is given as “All of the above are true for restriction enzymes”.

All the above options a., b. and c. correctly describe the properties of a restriction enzymes and they all are true with respect to restriction enzymes. Hence, the correct answer is option d.

Reasons for incorrect answer:

Option a. is given as, “are used to cut DNA into pieces for gene cloning”.

Restriction enzymes are widely used in the gene cloning experiments. They have the capability to cleave the DNA into small fragments. However, it is not the only property of a restriction enzyme. These enzymes are used by bacteria to prevent viral infections. They also produce sticky ends at the terminal ends of the produced DNA fragments. Hence, option a. is incorrect.

Option b. is given as, “are produced by bacterial cells to prevent viral infections”.

Restriction enzymes have the capability to prevent virus related infections in bacteria. However, they also have other important features such as they produce sticky ends at the terminal ends of DNA. They cleave the DNA to produce small fragments for gene cloning. Hence, option b. is incorrect.

Option c. is given as, “produce sticky ends on DNA fragments”.

The restriction enzymes are highly important enzymes in gene cloning experiments. They are able to produce sticky ends on DNA fragments. However, this is not the only importance of restriction enzymes. These enzymes cleave the DNA to produce small fragments. These fragments are used in gene cloning experiments. These enzymes are used to prevent viral infections in bacterial cells.  Hence, option c. is incorrect.

Option e. is given as, “Only a. and c. are true of restriction enzymes”.

Both option a. and c. are true for restriction enzymes. However option b. is also valid for the restriction enzymes. Hence, option e. is incorrect.

Hence, the options a., b., c., and e. are incorrect.

Conclusion

Therefore, all the mentioned reasons are true the restriction enzymes used in gene cloning experiments. They are used to cut DNA into fragments, produce sticky ends and are used by bacteria to prevent viral infections.