What amount of DNA yields a visible band on an agarose gel when stained with ethidium bromide?

Question

How much plasmid DNA do I need to load on a gel to be able to see sharp bands under UV light? What is the approximate range?
Any molecular biologists here?

Answer 1

It depends on the size of the DNA. If the gel is post-stained w/ 5 ug/mL EB, app. 50 ng DNA can be seen for the DNA ~100 bp. For larger sire of DNA >5 kb, the mimiunal visable DNA is lower, ~25-40 ng DNA can be seen.

Answer 2

Plasmid Dna On Agarose Gel

Answer 3

In addition to the concentration of EtBr used in the gel, the size of the fragment is also a factor. Here is a link to a lab where 1ug of restricted lambda DNA is loaded on a gel. The two smallest bands, which correspond to amounts less than 0.04 micrograms, are sometimes not visible. At any rate 1ug of DNA on a mini gel would light up like the sun, so I would say that the smallest amount of DNA still visible on a mini gel would be somewhere around 0.02 micrograms or about 20 nanograms.

http://www.accessexcellence.org/AE/AEC/AEF/1996/brown_dna.html

Answer 4

The loading directions for most DNA mass ladders are such that bands of 40 nanograms are easily visible. 125 nanograms gives a really bright signal.

Plasmids are easy to image and if you want a tight band, you should run only a small amount in wide wells. If you linearized the plasmid, then all the DNA should run in one band. You should load no more than 100 ng and see it easily. Load too much and then you'd get a smear.

Answer 5

EtBr agarose gel is very deadly to mitochondria( the energy producing parts in your cells). Since I'm not actually the board of chemistry I'm guessing your hand might be very weak. If I were you I would seek medical help immediately. Hope it works out ok. next time remember the gloves.

Answer 6

It's a hard question. I work at a lab at UCSF and at Johns Hopkins. "Visible" is kind of a vague word. It depends somewhat on the concentration of your gel and even more on the concentration of your EB.

Usually, our DNA is made at about 4 ug/ul concentration. We load 4 ul of it into our wells, and that produces a pretty good band, so im guessing maybe 15-20 ug total? You can run some gels at various amounts and see which one your like.

By the way, ug= microgram, just fyi.