Uncut lambda DNA showing bands??

Knepper, Marc A MKNEPPER at NMU.EDU
Mon Oct 16 19:53:10 EST 1995

Leo Schalkwyk asks:                                                             
>Did the host strain have any plasmids?                                         
>Leo Schalkwyk                                                                  
No. Unfortunately, I have already thought of that. Thanks for asking,           
Marc Knepper                                                                    
mknepper at nmu.edu                                                                
>In article <13OCT95.12834296.0015.MUSIC at NMU.EDU> you write:                    
>>Dear Netters:                                                                 
>>Here's a puzzle for you: I purified some lambda DNA + insert using a          
>>QIAGEN column, then ran 1 ug on a gel. Instead of seeing one intense          
>>band near the top, there were four distinct bands! I loaded some more of      
>>the DNA on the gel in another slot just to make sure this is what I was       
>>seeing. Then I did a digest with three different enzymes. All of the          
>>expected bands for each enzyme showed up on the gel, and it appears that      
>>the bands I'm seeing in the uncut DNA do not interfere with digestion.        
>>Has anybody else ever seen anything like this? Contamination with             
>>restriction enzymes could be ruled out since the DNA was placed at -4C        
>>immediately after purification, was taken out to use on the gel and           
>>returned immediately to the freezer. Any comments or ideas as to what         
>>this might be? Is it possible that it could be the left and right arms +      
>>insert showing up, or supercoiling? This has really baffled me? I would       
>>appreciate any help you can give. Thank you in advance.                       
>>Marc Knepper                                                                  
>>mknepper at nmu.edu                                                              

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