Are you attempting to check the ligation process or are you transforming the plasmid in cells then screening for positive colonies? What plasmid are you using?

When I ligate into Pgem Teasy vector I use xgal for blue white screening and then use primers for the t7 and sp6 polymerase sites to determine if i have a product.

if you are checking just a small ligation for example 10ul if my not have a strong enough signal to be detected on a gel.

I try to see the ligation process (vector+insert) before I perform the transformation. I agree that the amount my be not enough, however if I run the same amount of products before ligation I can observe them.

I don't think it's the best idea to check your ligation reactions on agarose gel before transformation and then worry if the correct sized band is not seen. What if the ligation reaction is not that efficient and you don't actually have enough ligated DNA to visualize on agarose gel??? The easier way would be to just transform it and then check the colonies the next day. Even if you have one molecule of ligated vector+insert, that should, in principle, give you one colony, if it has got transformed into an E coli cell.. And once you have your clone you really don't wanna worry about how well your ligation reaction was or how many colonies you had on the ligation plates. :)

Generally ligation doesn't occur between every molecules of DNA added.So it might be possible that the amount of sample  added by you on agarose gel might not contain ligated product. 

My suggestion would be, you go for transformation and then check the colonies for your product of interest.

Hi,

I second the opinions and responses given by the researchers, above. It is advisable to perform the agarose gel check after the transformation process.