MCQ of the Day

A medical student becomes interested in genetic cloning.  He has to do Polymerase chain reaction during various investigations.  Almost all Polymerase reactions invlove a heat stable DNA polymerase which is an enzyme originally derived from the bacterium Thermus aquaticus.  What does this enzyme do?

1. Assembles a new DNA strand from nucleotides
2. DNA melting
3. Primers manufacture
4. Shorten the DNA strand
5. Thermal cycling
    

 

 

 

 

 

 

 

 

 

 

Answer:a

Explanation:

Taq Polymerase is the heatstable DNA Polymerase that assembles the new DNA strand from the nucleotides.

A basic PCR set up require these components: DNA template, two Primers, Taq Polymerase, dNTPs, Buffer solution, Mg2, Mn2, K+.  Thermal cycling and DNA melting are used during the procedure.

(Choice b)  In DNA melting the two strands of DNA are separated at a high temperature.

(Choice c) Primers are short DNA fragments containing sequences complementary to the target region along with a DNA polymerase.

(Choice d) Elongation of the DNA segments is done by the enzyme.

(Choice e) Thermal cycling consists of cycles of repeated heating and cooling of the reaction for DNA melting and enzymatic replication of the DNA.

Educational Objective: 

The polymerase chain reaction (PCR) is  used  to amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence. It amplifies a focused segment of DNA, useful in the diagnosis and monitoring of genetic diseases, studying the function of targeted segment, DNA cloning for sequencing, DNA-based phylogeny, the identification of genetic fingerprints used in forensic sciences and DNA paternity testing and the diagnosis of infectious diseases.