DNA ISOLATION AND ANALYSIS - (May/18/2006 )

I have done the Lab using Gel Electrophoresis to study DNA Molecules
I used E.Coli and Salmon Sperm DNA and Standard I used Lambda Hind III
When I observe the gel on a UV light box

I seen E.Coli DNA has Bands but Salmon Sperm has Straight Single Band has big Smear
Of DNA.What is the Cause this Smearing?

All the bands and Smears of DNA samples are located right next to the wells and have not moved very far. What may have caused this?

I take it you are using undigested DNA samples and I suspect your E. coli DNA is actually plasmid DNA.

Chromosomal DNA is large 50-100kb in solution and is subject to shearing a bit, so with salmon sperm there are no bands, but high molecular weight DNA and you see the smear as there are a whole jhost of DNA of different lengths as reflected in the smear. Lambda DNA is less complex and you will see one band or two, as for E coli DNA you are seeing, I suspect it is plasmid DNA and like lambda, is low complexity, if it were chromosomal DNA you would see something like salmon sperm DNA

Nick