Question

Another application of the Polymerase Chain Reaction (PCR) is to screen samples for the presence of viruses. For example, remember the recent Ebola outbreak? In the US, if a patient is suspected of having clinical symptoms and is at high risk for exposure to Ebola virus, one technique to determine if that person is infected with Ebola is to send a blood sample for PCR based analysis. In this assay, many copies of specific DNA sequences are made in order to cross a detection threshold. Each Ebola virus is composed of single strand of RNA approximately 18,950 nucleotides long enclosed within a cylindrical viral envelope. In some laboratories, the first step might be to incubate samples with the enzyme Reverse Transcriptase. Why might this be? Choose all that apply.
A.The polymerase chain reaction is identical to all transcription reactions.

B.DNA is often the starting material for PCR so the viral genome is first transcribed into RNA.

C.DNA is often the starting material for PCR so the viral genome is first reverse transcribed into DNA.

D.In PCR, RNA primers bind to specific regions of DNA not RNA so the RNA must first be converted to DNA.


The polymerase used in PCR is called Taq polymerase and is isolated from the hot pool bacteria, Thermus aquaticus.
Why would human polymerase not be suitable for PCR based methods to determine if infection with Ebola had occured? Choose all that apply.

A.Human polymerase would not recognize viral DNA.

B.It is unethical to harvest human polymerase.

C.Human polymerase is much larger and more complicated as compared to bacterial polymerase.

D.Human polymerase would denature under the conditions of PCR.

E.Human polymerase would get infected by Ebola DNA and not catalyze the reaction.

Answer 1

Answer:

For the 1st part, the correct answer is option C.  

In a polymerase chain reaction, the amplification of DNA template takes place not RNA. So, prior to going into the process, there is a need to initially convert RNA into DNA with the help of an enzyme reverse transcriptase.  

For the 2nd part, the correct answer is option D.  

The suitable temperature for human DNA polymerase is 37 degrees Celsius, and it gets denatured at greater temperatures. As PCR runs at exceedingly high temperature like 95 degrees Celsius, only Taq DNA polymerase can withstand the temperature. Thus, normal DNA polymerase cannot be utilized in the PCR reactions.