For genomic DNA, it is quite normal and you can not do anythings.

For plasmidic DNA, it might be degradation....

Yes, DNA isolated is a bit degraded (fragmented). No worries DNA is fine you can happily work with it. I believe these are your fish samples. Main problem how did you store the tissue, from which part you isolated? All these matters a lot. If tissue is not stored properly or very old tissue you get that kind of results. While isolating DNA you have to a bit careful. If you have patience you can see from my answers about DNA isolation (pictures posted) because tissue is not stored properly it is infected and degraded.

I hope you do not get any problem with it you get nice results.

Cheers!

Owais,

What are your DNA samples (i.e., genomic DNA, plasmid DNA, PCR products) and what are the lengths of the DNA markers?

@Gary

Owais clearly mentioned "Why are my DNA samples smearing?"

I believe they are DNA samples certainly genomic DNA. Neither plasmid nor PCR products.

Jetty,

That is correct, they are DNA samples, but what kind of DNA samples is my question (I am not going to assume what kind of DNA they are), and knowing the markers length will help determine that as well.

@ Gary,

i used Lambda DNA/EcoRI+HindIII Marker , it is genomic DNA isolated from fins and muscle tissues of fish, with base pair length of apx 21226.

@Jetty, @Roche,

so it means i can use these DNA samples for PCR with out any problem

Certainly you can use. That was the reason I mentioned if you check the DNA profiles I posted. Though they are degraded they work. I say your samples are far better than the pictures I put on RG. Certainly they should work. what ever you want to do, do carefully.

Yes, this type of degradation can occur and is not necessarily a bad sign, if you can use.

What is important is the care you have with you process your samples to prevent further degradation and action of enzymes that can degrade DNA

Owais,

I agree with everyone, the DNA is useable as is but you did get some degradation during the isolation of the genomic DNA. Next time, I would try a DNA isolation method that uses GuHCl, Sigma and other companies sell kits that use GuHCl and spin columns to isolate high quality genomic DNA that is nuclease free.

See the link below for gel pictures of mammalian genomic DNA isolated using the Sigma kit:

http://www.sigmaaldrich.com/life-science/molecular-biology/dna-and-rna-purification/mammalian-genomic-dna-miniprep-kit.html

You loaded too many DNA. Try to dilute and load 20 - 50 ng DNA per lane.

Beyond DNA degradation treat your samples with PK to digest all the proteins and make sure there is no protein contamination. Also treat your samples with RNase A appropriately. That should help.

"it is genomic DNA isolated from fins and muscle tissues of fish". I assume that you use proteinase K to treat the samples first. Here is a solution recipe for tail lysis buffer (TL) and column binding buffer (BD) for gDNA isolation for mouse tail. You can leave the samples in this solution at 55*C for overnight or several hours till tissue is completely digested. Then add 3 volume of N3 binding buffer (or PB buffer). Mix and load the whole thing on any silica membrane based spin columns---> spin and discard the flow though and add 600ul of 80% ethanol to wash the column. Dry the column and elute with preheated (65*C) ddH2O. You should get high quality gDNA!

Here is the link to get bulk DNA mini spin columns ($36 for 100 DNA columns, or $59 for 100 RNA columns):

http://www.enzymax.net/columns/mini_column_DNA.htm

TL Buffer :

100 mM Tris-HCl, pH8.5

10 mM EDTA

200 mM NaCl

0.2% SDS to 0.5%SDS

*50 g/ml proteinase K (2.5 l/ml of 20 mg/ml stock, add just before use)—add this before use

N3 ( DNA binding): 4 M guanidine hydrochloride (GuHCl), and 0.5 M potassium acetate, pH 4.2 (Qiagen Cat#19064, 500 ml)

PB Buffer (binding buffer 2): 5 M guanidine hydrochloride, 20 mM Tris-HCl, pH 6.6 (25oC) in 80% ethanol. (Qiagen Cat#19066, 500 ml).

Good luck!

Hi Michelle,

Can you correct the "micro symbol" to just "u", since there is a strange font for the micro symbol. Good link.

Oops, sorry about this. Thanks Gary!

TL Buffer (Binding buffer):

100 mM Tris-HCl, pH8.5

10 mM EDTA

200 mM NaCl

0.2% SDS to 0.5%SDS

*50 ug/ml proteinase K (2.5 ul/ml of 20 mg/ml stock, add just before use)—add this before use

You might be using very old tissue sample. Old sample can yield in smeared DNA. Isolate your DNA from freshly taken samples. We had the same problem with our DNA sample. 

RNA contamination, ran gel too fast (MW markers are smiling), samples are partially degraded due to age/storage conditions or were not denatured fast enough at a low temperature and so allowed DNAse to partially degrade the samples.