Well, if you prepare DNA, whether the material was frozen or not, you will always obtain fragments of different length and sometimes degradation and this will be the smear on the gel. If you digest the DNA with EcoRI or another restriction enzyme in the smear distinct bands will appear but you will still see the smear.

The reason for the existence of SNP or polymorphisms in the DNA is simple. The DNA is exposed to several noxe, like radiation, radicals ... and the repair mechanisms are not perfect. So sometimes a base change appears and is transmitted, over time this change spread in the population. Other bigger changes appear during the meiosis.

Dear Mr Besari,

I can provide some guidance on what SNPs are, but am unable to help with the second question.

A good source of genetics information is OMIM - Online Mendelian Inheritance in Man. Best of luck.

http://www.ncbi.nlm.nih.gov/books/NBK21088/

http://ghr.nlm.nih.gov/handbook/genomicresearch/snp

thankyou Attiyah Omerjee for your help :)

Well, if you prepare DNA, whether the material was frozen or not, you will always obtain fragments of different length and sometimes degradation and this will be the smear on the gel. If you digest the DNA with EcoRI or another restriction enzyme in the smear distinct bands will appear but you will still see the smear.

The reason for the existence of SNP or polymorphisms in the DNA is simple. The DNA is exposed to several noxe, like radiation, radicals ... and the repair mechanisms are not perfect. So sometimes a base change appears and is transmitted, over time this change spread in the population. Other bigger changes appear during the meiosis.

Further to Michael's answer degradation of DNA is very common in preparation from random enzymatic nuclease cutting on sample thawing or freeze damage on storage and even physical shock because DNA is a long thin molecule and vigorous shaking or mixing in the preparation method can cause degradation. Your picture looks good and typical ( either overloaded or too much salt in the last lane) and at low molecular weight you may also see rNA fluorescing but in your picture I think this has run off the end of the gel

well, thank you Mr. Michael and Mr. Paul.. From the picture I attached above.. does this genome has size? I mean, because the bands are above the 10.000bp, I couldn't represent the size exactly.. so, what is the size of this genome?

It is not possible to give a genome size because I do not know what orgnism this is and whether it has chromosomes and how many. Also agarose gel is not good at separating large sizes of DNA well and I would expect the DNA to be sheared into random but large fragments during its Isolation. Posiibly running a hindiii lambda ladder might give some idea of the average size pof your fragments as it has a 23kb band   but if your next step is restriction digestion or PCR then the size of your dna is just fine. It looks like a good preparation

well, that's true. the next step is PCR, then purification with Promega Wizard SV Gel and PCR Clean-Up System, then I do RFLP. and the results just fine and have good visible bands. thankyou so much Mr. Paul..

If you obtain a single band in your PCR you can digest it directly without prior clean-up; we just dilute the PCR 1:1 with a solution containing 2x restriction buffer + enzyme, in most cases its running well.