gel

[Shirley]

I have made some competent cells and transform them with a vector. Then I did a plasmid isolation. The DNA concentration is 100ug/ml. I run a gel but no band is detected. So you think my competent cells are really competent?

[canalon]

There are plenty of things that may have gone wrong:
- competent cells as you said,
but also :
- plasmid isolation
- Selection of transformants

Without more details I can't help.

[sdekivit]

There are plenty of things that may have gone wrong:
- competent cells as you said,
but also :
- plasmid isolation
- Selection of transformants

Without more details I can't help.

or the gel isn't made properly

[canalon]

There are plenty of things that may have gone wrong:
- competent cells as you said,
but also :
- plasmid isolation
- Selection of transformants

Without more details I can't help.

or the gel isn't made properly

True enough.
Run in water? (I did that once, it melted )
Forget to stain?
Did not load? I once had a problem with a loading buffer that wasn't dense enough to make the solution go into the gel. It would just stay on top and leak out )