Question

How do you interpret gel electrophoresis results?

Answer 1

The further down the bands are, the more they traveled, thus the less resistance they had, thus the smaller they were.

Explanation:

DNA has some mutations in in, some of these are called point mutations, which are single nucleotide changes. If these occur with a specific sequence, called a restriction site, an enzyme known as a restriction enzyme will cut the DNA at that point. Say a mutation of a gene allows a restriction enzyme to cut the DNA in 2 pieces, a DNA strand with that mutation will be cut into to smaller pieces, and a DNA strand without the mutation will not be cut, and will remain as one big piece.
When the current is applied to the gel, the DNA (because it is negatively charged due to its phosphate backbone) will be pushed down the gel. The longer stand will face more resistance, and thus move less than the two shorter strands. If the exact restriction sites are known, then by comparing it to a reference set of predetermined lengths, usually in one of the side wells, the exact mutations can be determined.