What' the real length of normal genomic DNA

[Greg Smith]

In article <9509048128.AA812835339 at ccmail.llu.edu> oRutebuka at CCMAIL.LLU.EDU ("oRutebuka") writes:
>From: oRutebuka at CCMAIL.LLU.EDU ("oRutebuka")
>Subject: Re: What' the real length of normal genomic DNA
>Date: 4 Oct 1995 17:14:00 -0700

It seems that my points were misunderstood. Maybe I should have put my 
question in a different way. What I really like to know is the length, or 
range of length of  DNA fragments prepared by normal "genomic DNA" methods.  I 
am not talking about intact molecules here, but the DNA fragments (revealed by 
gels)  being through the process of "DNA isolation".  

Actually the genome size is not an issue here as we are dicussing the DNA 
fragments. "Genomic", when used for DNA isolation methods, implies that all or 
most of the DNA within the genome is represented. You are 100% right that 
gels, pulse field or not, are not normally suitable for estimating eucaryotic 
genome sizes. 

>     You will find that I am not answering your question but you may 
>     realize that I am a little bit expanding it.  We talk about DNA 
>     molecule.  To my understanding there is not such thing as a DNA 
>     molecule.  Consider a "molecule" of DNA.  How many atoms?  You see 
>     when we talk about a molecule of water (H2O) we know we have three 
>     atoms.  In the case of DNA we rather talk about genomic size.  We are 
>     counting base pairs and this depends on a species.  The genome size 
>     can be estimated from several methods including Pulsed-Field Gel 
>     Electrophoresis.  In many eucaryotes, this genomic DNA may be too 
>     large even to be resolved by PFGE thus restriction by endonucleases.
>     
>     


>______________________________ Reply Separator _________________________________
>Subject: What' the real length of normal genomic DNA
>Author:  g.smith at mailbox.uq.oz.au (Greg Smith) at InternetMail
>Date:    10/3/95 10:08 AM


>Dear netters,

>I'm wondering what the actual length (or range) the genomic DNA has. 

> Of course the normal gel electrophoresis cannt handle it properly, so the 
>length is supposed to be around of 50 kb. But all the references with pulse 
>field gel  I have seen only display genomic DNA prepared from gel block or 
>bead, with lengths 1mb or above.  Has anybody seen the pulse field  gel photo 
>of eucaryote genomic DNA prepared with conventional method?


>S. Weining
>s.weining at mailbox.uq.oz.au
>Queensland Ag Biotech Centre
>Gehrmann Labs
>St Lucia 4072
>Australia