1. No, people don't use DNA ladders for PCR positive control. DNA ladders provide you the information of the sizes of your DNA fragments on the gel.

2. When doing PCR, controls (Positive and Negative) should be included and performed side by side with your DNA sample tube during the whole PCR process. Positive control also let you know that your PCR set up and the condition of the machine are ok, if the expect band is amplified. 

I think isn't the best option. You positive control need to be the organism that you are looking for in you PCR. The genomic DNA hadn't the same weight that the result of PCR reaction.  

No you don´t, DNA ladder is not a positive control, is a reference for the size of your PCR products

With what kind of sample are you working?, DNA ladder is in many cases synthetic the sequence is unknown or viral, your positive control need to have the corresponding sequence of  both primers in PCR.

No not at all. how can you use a DNA ladder as a positive control in your PCR reactions??? you should have DNA/cDNA from control sample for the PCR of positive control.

This is not a good question and can be be answered appropriately. What is your product from the PCR? Do you know the size of the right product? However, in general I will say it is not a good idea to use DNA ladder as your control.

1. No, people don't use DNA ladders for PCR positive control. DNA ladders provide you the information of the sizes of your DNA fragments on the gel.

2. When doing PCR, controls (Positive and Negative) should be included and performed side by side with your DNA sample tube during the whole PCR process. Positive control also let you know that your PCR set up and the condition of the machine are ok, if the expect band is amplified. 

positive control is something which verifies all your step working through out the experiment 

so DNA ladder is not the option for your positive control

you sure need a strain with target gene in it

Dont use ladder as positive control. totally wrong view. 

I think PCR positive control is the DNA to which your primers can bind and give amplification. Ladder is the synthetic DNA which is having fragments of specific sizes. But the sequence is never known. Hence I suggest that you must not use ladder as positive control.

DNA ladder can't be a positive control in your PCR reaction.

For positive control ideally genomic DNA or cDNA is used as template, which you use to amplify your gene of interest. For primers in positive control use the primers for any gene that has worked in PCR reaction previously. Alternatively, you may also use isolated plasmid or PCR amplified product as the template in positive control PCR reaction.

Definitely not!

You must use a nucleic acid of a material which had previously given a positive reaction, just as Vishal (above) had written.

I agree with Vishal Singh Negi. Plasmid or pcr product can be used as positive control.

in case of RT PCR, you can  generate in vitro transcript as wel

Absolutely not..

I would agree with the above comments. It's not a good idea at all.

The best positive control would be the genomic or cDNA that should (for sure) give the band that you will compare rest of the samples with. 

I agree with your suggestions. But for in house lab study, it will be ok. Genomic dna from clinical samples will have low concn and might not give consistent results.

Best option is cloning then.

A positive control is something in which you are sure about the presence of the gene which you are amplifying in your samples. The cells of the organism or gDNA extracted from the organism can serve to be positive control. A synthetic DNA ladder cannot be used for this purpose. 

Kindly elaborate on which bio-agent you are working on and which gene are you amplifying, It will help others to help you better. :-)

no u can not use.

No need to use ladder for DNA. Just use control DNA to evaluate the gel electrophoresis

I would like to stress a simple point here to Noha said,

You should have mention for what purpose you want to use ladder as a positive control.

You can use ladder as a marker when you just going to run a whole DNA into a gel to see the size of genome. like 10kb or 1000kb ladder.

In the case of small bacteria or plasmids. when you dont have another set of same dna which is confirmed as PC by any standard method like PCR.

I Hope you could get some valuable answer, if you given us a clear detailed question.

all the best ...

Hi there!

I agree with the above. Don't get confused on this. A ladder can only be run on the gel alongside your amplified samples in order to check for the amplicons' sizes. The only other use of a ladder when run on the gel is that you can roughly quantify your sample Please note: You cannot determine the quantity of your amplicon in precision by doing this, it only provides a very rough estimation, that's all.

BW

Nikos

DNA ladder is used for determination of band size and confirmarion of intrested band size. Dont confuse about this and use positive and negative control to complete your expriment.

I agree with Magdalena Monika Owczarek and Yuan-Yeu Yau.

For positive control you must done already PCR process again with the sample that has 'wanted' fragment DNA.

It is not the best option. Ladder DNA is only a help for distinguish the size of your sample but it is not a positive control of your PCR at all. The positive control is used to ensure that all the reactives of you PCR are working well. I hope it can be helpful for you

positive control for samples is used as a quality control of the system you are working with, in PCR it is just to ensure that the conditions you add in the PCR mix are fine and what is seen in your gel is the real amplified bands and not anything else. it helps you identify problem in PCR, e.g. if you got no band in your positive control that tells you that there is a problem with your experiment

I agree with Magdalena Monika Owczarek and Yuan-Yeu Yau.

A  DNA ladder is used to identify the approximate size of a molecule run on a gel during electrophoresis, using the principle that molecular weight is inversely proportional to migration rate through a gel matrix. Therefore when used in gel electrophoresis, it provides a  sort of logarithmic scale by which to estimate the size of the other fragments. So you need to set up your positive as well as negative controls as suggested by Mahboubeh Mostafaei and Esteban Orenes-Pinero.

Best luck

Innovative idea. But you will have the only problem... your primer would not be specific for the ladder DNA. If the primer doesn't prime, then I guess PCR will always be negative! Right?

I agree with everyone, but here is another way of thinking about it. Your ladder is a postive control, but only for your gel, not your PCR. While it will help you to evaluate whether or not your gel is capable of giving you results.

But I agree with the earlier suggestion that your positive PCR control should be organism specific, tried and true.