possible errata in Examkrackers Biology book??

[Monkeymaniac]

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On page 35 of the book (5th edition), it describes the method of PCR. It states that "In PCR, the double strand of DNA to be cloned is placed in a mixture with many copies of two DNA primers, one for each strand." Is there such thing as "DNA primer"? At the bottom of the same page, an illustration is provided, and pictures of Primers are labeled as RNA Primers instead. So are RNA Primers used in PCR or DNA Primers? I am confused. Did anyone find this odd?

 

[rskhan29]

I don't think it is an error. DNA primers are usually used in PCR.

 

[engineeredout]

T = 5 seconds:

http://en.wikipedia.org/wiki/Polymerase_chain_reaction

Almost all PCR applications employ a heat-stable DNA polymerase, such as Taq polymerase, an enzyme originally isolated from the bacterium Thermus aquaticus. This DNA polymerase enzymatically assembles a new DNA strand from DNA building blocks, the nucleotides, using single-stranded DNA as template and DNA oligonucleotides (also called DNA primers) required for initiation of DNA synthesis

 

[Lukkie]

yes for PCR we use DNA primers.

 

[Phlame217]

For the 300+ hours i spent using a PCR, DNA primers are used...

 

[Monkeymaniac]

Ok, thank you for the answers. Then do we ever use RNA primers in PCR at all? I just don't like how the book talks about DNA primers and then labels pictures of primers as RNA primers.

 

[Lukkie]

i dont think so. RNA is pretty unstable and primers would degrade pretty quick, whereas DNA primers can be stored for years

 

[futuredoctor10]

Yeah must be an errata in the book!

There should be a list of the Errata on SDN for various exam prep company's books?

 

[Vihsadas]

i dont think so. RNA is pretty unstable and primers would degrade pretty quick, whereas DNA primers can be stored for years

This is true. There are two common ways to perform PCR:

1) Use DNA primers and harvested DNA.
In this method you harvest DNA, add your primers and PCR reagents, and then amplify! You can use this to identify whether a certain gene, or a certain mutation type of a gene exists within a genome.

2) Use DNA primers, reverse transcriptase and harvested RNA.
In this method you use reverse transcriptase enzyme to create cDNA from harvested RNA within the PCR reaction mixture. You can use this method to identify the genes that are being transcribed to RNA in your cells. This allows you to differentiate gene expression (transcription) from gene presence in the genome.

The next step would be to run a western blot on the protein to see if the actual protein is being expressed from the RNA that you detected.

So, yes, you really only use DNA primers in PCR. I'm not certain is RNA primers have been used, but RT-PCR (reverse transcriptase PCR) uses DNA primers.

 

[Phlame217]

RT-PCR actually stands for "Real-Time" becuase well, its done in real time versus the 3 base assay approach with the gel plates...

 

[Vihsadas]

RT-PCR actually stands for "Real-Time" becuase well, its done in real time versus the 3 base assay approach with the gel plates...

There's actually a discrepancy with the nomenclature. RT-PCR was originally coined to mean "Real-Time PCR" which as you know is a quantitative method. Recently, however, there has been confusion about what to call "Reverse Transcriptase PCR" since it would also be RT-PCR. To solve this, more and more scientists are referring to Real-Time PCR as "Quantitative PCR". So, it's becoming more common to see "RT-PCR" as meaning "Reverse Transcriptase PCR" and "Real-time PCR" or "quantitative PCR" shortened to q-PCR.