gel electrophoresis question

[kabuto]

hi, i get an assignment that ask us to name the advantage of using gel ellectrophoresis to identify DNA molecules
all i can think of is that electrophoresis
1 separates them into different size, shape and charge
2 dna is negatively charged so can hybridise

what are the other advantages??

[weesper]

All it does is seperate according to size, not to charge per se because charge is determined by size. DNA forms complementary bonds but not because it is negatively charged (is because of the phosphate moiety). Advantage is separation according to size, thereafter you can digest the fragment out of the gel and sequence it for example which would allow you to identify it directly.