Gel Electrophoresis

[regeneration]

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Hi guys,

A bit confused: I understand that a smaller fragment (of DNA or protein w/ SDS) is supposed to run faster in a gel than a larger fragment; this is because the pores in the gel allow for smaller fragments to move more quickly.

However, why is it that larger fragments with more charge don't have a greater attraction to the positively charged anode? I was thinking that since the larger fragments have more charge, they should have more force pulling them.

Thanks.

 

[brlin]

From what I understand, they do have more force pulling on them, but their size difference plays a bigger factor in migration rate than force from the extra negative charge.