Q20-2TYU. - Campbell Biology

Question

Which of the following tools of DNA technology is incorrectly paired with its use? 

(A) electrophoresis—separation of DNA fragments

(B) DNA ligase—cutting DNA, creating sticky ends of restriction

fragments

(C) DNA polymerase—polymerase chain reaction to amplify

sections of DNA

(D) reverse transcriptase—production of cDNA from

mRNA

Step-by-Step Solution

Answer

 

(A) The option “electrophoresis—separation of DNA fragments” is false.

(B) The option “DNA ligase—cutting DNA, creating sticky ends of restriction fragments” is true.

(C) The option “DNA polymerase—polymerase chain reaction to amplify

sections of DNA” is false.

(D)The option “reverse transcriptase—production of cDNA from mRNA” is false.

 

Step 1: Tools of DNA technology

DNA technology is the molecular technique that involves finding the desired DNA fragments from the genome of an organism, inserting them in a suitable vector, and forming recombinant DNA. After this, it is multiplied in a host. 

 

The task of DNA technology is not accomplished without using some tools that are mandatory to use. These tools constitute a vector, restriction enzymes, other enzymes like DNA ligase, DNA polymerase, reverse transcriptase, a host organism, and gel electrophoresis.

Step 2: Explanation of option ‘(A)’

Electrophoresis is a technique that involves the use of a gel matrix to separate DNA and proteins on the basis of the size of molecules and the electric charge present on them.

Thus, electrophoresis and separation of DNA fragments are correctly paired.

Therefore, the given option is false.

Step 3: Explanation of option ‘(B)’

DNA ligase is an enzyme that catalyzes the synthesis reaction that involves the formation of a phosphodiester bond between two DNA strands and joining them. DNA molecules are cut and digested by using restriction enzymes that also create sticky ends in DNA fragments.

 

Thus, cutting DNA and creating sticky ends in DNA fragments do not involve DNA ligases.

Therefore, the given option is true.

Step 4: Explanation of option ‘(C)’

DNA polymerases are enzymes involved in genome replication and maintenance and are also used in DNA technology to amplify the desired DNA fragments. They are used for DNA cloning, polymerase chain reaction, and genome sequencing.

Thus, DNA polymerases are used to amplify a section of DNA in the polymerase chain reaction.  

Therefore, the given statement is false.

Step 5: Explanation of option ‘(D)’

Reverse transcriptase is the enzyme that catalyzes the reverse process of central dogma that is reverse transcription. It makes complementary DNA copies of an RNA molecule.

Thus, reverse transcriptase synthesizes DNA copies from mRNA that is called complementary DNA.  

Therefore, the given statement is false.