Gel electrophoresis prob (ethiduim bromide)

[Gamewizard]

Hi everyone,

 

ok this is my first thread on here. I am having problems with one of the questions, if anyone could give me some advice/hint on it.

 

A DNA molecule is 48000 base pairs long. it is cut by a restriction enzyme (Hind III) into 8 basepairs, i m supposed to see 8 bands on the gel photograph but can only see 6.

Ok, my teacher said this is because we used ethiduim bromide as a stain, but i dont understand how bromide is related to any of this, i have searched properties of bromide on the net but cant find anything related

 

i would be grateful if anyone could help

[CharonY]

I suppose you mean 8 fragments instead of 8 base pairs? I do not think that the teacher gave the correct answer, but to be sure, what sizes did you expect?

[Gamewizard]

I suppose you mean 8 fragments instead of 8 base pairs? I do not think that the teacher gave the correct answer, but to be sure, what sizes did you expect?

 

yes sorry i meant 8 fragments. I am not sure about the sizes

[CharonY]

There are several reasons why they may be invisible. The most likely one is that they may be not resolved in the gel because they are either too long, too short or too close in size from each other.

It is a matter of the resolving power of the gel rather than the stain, though.

Stains come in when it comes to sensitivity. However, a proper ethidium bromide stain tends to be very sensitive to begin with and if you see some bands, the rest should be visible, too. Exceptions are very small molecules, but chances are that they are outside the resolving power of the gel, anyway.

Edited March 23, 2010 by CharonY

[Gamewizard]

There are several reasons why they may be invisible. The most likely one is that they may be not resolved in the gel because they are either too long, too short or too close in size from each other.

It is a matter of the resolving power of the gel rather than the stain, though.

Stains come in when it comes to sensitivity. However, a proper ethidium bromide stain tends to be very sensitive to begin with and if you see some bands, the rest should be visible, too. Exceptions are very small molecules, but chances are that they are outside the resolving power of the gel, anyway.

 

Thanks Charon