Real-Time RT-PCR one-step and two step issue - (Feb/26/2009 )

I'm trying to buy a SYBR Green RT-PCR kit for our RotorGene 6000 5 Plex HRM but I have some questions to ask.

for the moment I need to detect expression of mRNA in our cells so definitely I would prefer to buy a one-step kit, but the question is that in case I finish working with mRNA and then decide to work with DNA sample, can I still use the same one-step RT-PCR kit? because the first cDNA snthesis step shouldn't be interfering with my DNA samples. am I right?...if not....then wouldn't it be better to buy a two-step kit?

I still haven't decided to buy from which company and I am aware that company issues are not for this subforum, but still I would appreciate if you guys could let me know where you buy your kits from?

In fact I don't know, because I never tried. But I ask myself, why do you want to spent more money than you have too? Why buying also RT-reagents when you don't need them?
Wow, wish I could affort that ... :-)

Good luck!

it's not really my fault.....the kit is for 400 reactions....Qiagen doesn't have less than that. that's why....don't mock me:D

also Quantace supplier doesn't give less than 250-reaction kits. it's their policy....so I HAVE TO go for those kits altough I don't want to.

Did not want to blame you :-)
And I better don't start talking about Qiagen....

I use Quantace and they also sell their SensiMix kit for 50reactions. You can downsize the reaction volume from 50µl to 25µl without any problem, so you would end up with 100 reactions. And you can order the same SYBR-green + Mastermix they use for their SensiMix seperately without the reverse trascription stuff.
But if you allready have bought the 400 reactions it's to late anyway.

All the best!

still haven't bought. waiting for qiagen quotation to compare with quantace. thank you anyway.

ahh, sorry, you are doing HRM, that's propably an other kit (saturating dye...)

Good luck!

In theory, the answer to the original question is that yes you can use the cDNA for downstream applications from the one-step kits, BUT, you will need to clean it up as the buffers/salt does funky things for downstream applications (at least it's been my experience). I just ended up doing the whole thing with Trizol and then RT manually as I had more flexibility and consistency (plus it saved a ton of money too Is the RT step a random hex/oligo dT or gene specific?

hi,

thanks for your reply.

Qiagen kit has a reverse trascriptase enzyme called Omniscript which ,I think, there is no need to use Oligo dT with it anymore. this enzyme enables cDNA synthesis from viral RNA too. the kit is not gene specific, but I would prefer not to do Trizol extraction for real-time pcr.....is it really reliable to use trizol extracts in real-time pcr?

I've heard of omniscript, but have not used it, and I'm assuming if there's not oligo dT and it transcribes viral RNA then it's most likely random hexamers (or nonamers). Omniscript by itself assumes that you already have purified your RNA (unless it's part of a generalized kit that incorporates it into a one step process).

It's a question of practice. In the past, I had to use Trizol as the incubation step in one of the qiagen kits was too long and I got used to using it and with an extra acid phenol extraction, I've had good results. However, the one-steps are definitely easier, especially with small sample sizes.

But, in response to the original question which was whether the 1st strand cDNA could be used for other purposes after the qRT PCR, the aswer is yes, but you will need to purifiy it in some manner.

Curtis on Mar 5 2009, 02:33 PM said: