RT-PCR is term used for "Reverse Transcription" PCR , where the starting genetic material in the PCR reaction is RNA ,where RNA is first transcribed in reverse into its DNA complement by reverse transcriptase enzyme. The new complementary DNA containing the reversed transcription will then be amplified using the traditional PCR or real-time PCR. and here if you proceed with traditional PCR you will read your results as "presence or absence" of the amplified gene product using agarose gel electrophoresis (No quantification).

While qPCR (Quantative PCR)or sometimes called digital PCR you have a qPCR machine and a fluorescent dye in your PCR reaction (Sybr green or Taqman Probe) that bind to your amplified gene product and give you a Ct value , which later on gives you an idea about the quantity or your RNA or DNA in your reaction depending on a standards used , in this case you are not in need to do gel electrophoresis to see your amplified pcr product.

so qPCR could be also RT-qPCR if you work on RNA or only qPCR if DNA is your starting genetic material.

qPCR is a quantitative PCR using a scale or standard curve. RTPCR is real time PCR and does not imply a quantitative analyses.

RT-PCR (Reverse Transcription-PCR): usually you start from RNA, reverse transcribing to cDNA, then do the PCR reaction (usually to measure gene expression)

qPCR (quantative-PCR): the amount of DNA after each cycle of replication is measured, usually using fluorescent dyes (used to quantitatively measure the amplification of DNA)

This two terms usually make confusion to beginners. In old published papers, they wrote RT-PCR but it was not reverse transcriptase PCR. They mentioned it as Real Time pcr. However, later, because of this confusion, all scientists agreed to write real time PCR as (qPCR) and for reverse transcriptase PCR as RT-qPCR. Therefore, nowadays RT-PCR is simply meant to reverse transcriptase reaction only for normal PCR. Therefore, if you are reading old papers, be careful to know how writers named their experiments. 

RT-PCR is term used for "Reverse Transcription" PCR , where the starting genetic material in the PCR reaction is RNA ,where RNA is first transcribed in reverse into its DNA complement by reverse transcriptase enzyme. The new complementary DNA containing the reversed transcription will then be amplified using the traditional PCR or real-time PCR. and here if you proceed with traditional PCR you will read your results as "presence or absence" of the amplified gene product using agarose gel electrophoresis (No quantification).

While qPCR (Quantative PCR)or sometimes called digital PCR you have a qPCR machine and a fluorescent dye in your PCR reaction (Sybr green or Taqman Probe) that bind to your amplified gene product and give you a Ct value , which later on gives you an idea about the quantity or your RNA or DNA in your reaction depending on a standards used , in this case you are not in need to do gel electrophoresis to see your amplified pcr product.

so qPCR could be also RT-qPCR if you work on RNA or only qPCR if DNA is your starting genetic material.

Thank You all of the researchers who contribute to my question. 

1. Both QPCR and RT-PCR are used in biotechnology and used for the production of multiple copies of DNA.

2.RT-PCR is used to amplify the reversed transcription of the DNA code where as the QPCR measures the amplification.

3.QPCR is quantitative in nature while RT-PCR is not

Dear Dr. Aqleem

i agree with all respected answers from all that mention above and

i can summery the different between them in these points:-

1.QPCR and RT-PCR are both terms used in biotechnology and utilized for the production of multiple copies of DNA. 2.RT-PCR is used to amplify the reversed transcription of the DNA code; QPCR measures the amplification. 3.RT-PCR is for amplification, while qPCR is for quantification. 4.QPCR is quantitative in nature, while RT-PCR is not.

i suggest you read this

Basic of quantitative real time PCR

Presentation Basic of quantitative real time PCR

good luck to you

RT-PCR can be used without qPCR, for example to enable molecular cloning, sequencing or simple detection of RNA. Conversely, qPCR can be used without RT-PCR, for example to quantify the copy number of a specific piece of DNA.

Mohamed Rasheed Gadalla sir I have bit confusion in one thing, I have to perform on an experiment where I need to quantify MT-DNA from plasma samples of humans and mice disease model, which one should I use and why? for mtDNA analysis, there is no need for performing RT PCR? plz reply.

Dear @ Deepika Gautam, for mtDNA you do not need an RT (reverse transcription) as it is already DNA. You can measure abundance/ copy number by simple qPCR, however even extracted from supposed cell free plasma, you might not get a lot of signal, but mtLeakage into plasma under certain stress situations has been reported. Article Increased plasma levels of circulating cell-free mitochondri...

You might find your answers in this article.

Does anyone know, if there is a difference in quality between qPCR and RT-qPCR, apart from the starting material.

Is one method likely to give you a stronger signal intensity (assuming florescent dye is the same)?

Thx!

Myriam Merz thank you so much mam.

Myriam Merz

The use of a qPCR or an RT-qPCR is really dependent on the starting material and the goal of the experiment/question.

However, if you would have an assay-design targeting, lets say the 16s rRNA of a specific bacteria and test this with both the RT-qPCR and the qPCR assay. You would find a significant increase in the RT-qPCR. This because the ribosomal RNA count (ranging from 6800-72000/E.coli) is many times larger compared to the number of gene copies (~5 / genome).

On the other side, if you would like to determine the viral load of a DNA virus (e.g. human papillomavirus). The results of the qPCR should be more reliable and the Cq value could be about the same as the RT-qPCR. Assuming mRNA isn't targeted by the primers..

To be short; there is no real straightforward answer, it depends :)

Maarten van der Salm

Thanks,

that was really informative.

I didnt even think of the rRNA.

Just to defend a little bit the classic PCR -followed by gel combo :) You don't get a nice quantity value but you could look at the intensity of the band and compare it to the ladder. That should get you some idea about the quantity.

RT-PCR is simply meant to reverse transcriptase reaction only for normal PCR.

What is the main difference between qRT-PCR and RT-qPCR ?

Mohamed Rasheed Gadalla Sir, your answer was awesome. cleared everything in one shot. Literally explained so nice

Hi everyone ..is there any difference between the primers designed for use in RT PCR & qRT PCR ?

@Marzie It would be really helpful if you could please justify why the primers used for RT PCR can't be used for qPCR?

As per my understanding, if you're doing the RT PCR using RNA specific primer(s) (rather than oligodT or Random hexamers), you should be able to use the same primers for qPCR, given they satisfy the primer criteria for the qPCR.

Just to add more weightage to the above statement, the primers that you have used for making cDNA is now the part of cDNA strands and hence those primers can again bind to their complementary strand(s) during qPCR amplification.

Please feel free to correct me if I am wrong.