What is the gt in lambda gt10 or gt11?

Brian Smith-White smithwhi at students.msu.edu
Fri Mar 11 18:18:00 EST 1994


In Article <2lkvg9$pen at news.acns.nwu.edu> "h-seifert at nwu.edu (Hank Seifert)" says:
> In article <riggs-080394105259 at 192.138.220.168> riggs at neb.com (Paul Riggs) writes:
> >In article <2l2fk4$s5q at news.acns.nwu.edu>, h-seifert at nwu.edu (Hank Seifert)
> >wrote:
> >
> >> >I think it means "generalized transducing," by analogy to phage
> >> >transduction by P1, P22, etc.
> >> >
> >> >______
> >> >Paul Riggs
> >>
> >> I don't think so since these are specialized transducing phages
> >> not generalized!
> >> Hank Seifert
> >> Northwestern University
> >
> >Generalized means "can transduce any piece of DNA," such as pieces of the
> >chromosome or, in this case, any restriction fragment. Specialized means
> >the phage transduces the same marker all the time, such as lambda-gal and
> >lamda-bio specialized transducing phage.
> >______
> >Paul Riggs
> >New England Biolabs
> >riggs at neb.com
> 
> Right you are.  I was just talking off the top of my head and 
> as usual was wrong.  However in the spirit of discussion, 
> should terms from genetics be used to describe new techniques 
> that arise from molecular biology?  The process of transducing 
> a new piece of DNA is not unique to the lambda-gt-series of 
> bacteriophage but also applies to M13 phage and all other phage 
> derived cloning vectors.  None of these vectors have a 'gt' 
> designation. 
The tradition of including 'gt' as part of the name of a particular phage
strain was a part of the history of lambda phage genetics whereas this
tradition was absent in M13. This is simply because only lambda was ever
able to demonstrate generalized transduction prior to the age of in vitro 
manipulation. If you use M13 to clone - in contrast to subcloning - you
deserve all the problems you encounter.
The process of cloning into a phage 
> vector is very distinct from generalized transduction 
Is it? Just because you perform all but one of the steps in a cell-free
environment does not justify overlooking the identity with the in vivo 
process. Otherwise one would have to create a new name for the process of 
encapsidating the lambda genomes in vitro to distinguish that from the name
originally developed for the process in vivo - packaging the phage genome.
Have you?
and could 
> result in the new generations of researchers, 
> many of whom never heard of generalized transduction, thinking that 
> the term is specific for cloning.  The 'gt' label was good 
> advertising for Young and Davis, but is it good terminology?
The vocabulary is not good with respect to gt10 since the presence of an
insert renders the phage incapable of forming a lysogen in the absence of cI
protein supplied in trans. The ability to form a lysogen is an obligatory 
intermediate in generalized transduction by lambda. However Young and Davis 
followed a tradition initiated by others in the development of cloning 
vectors which have been supeceded by those currently in vogue with their 
trademarked names. (Don't get me started about this silliness.)
>      I'm also concerned about the use 
> of other genetic terms in this context.  Genetic 
> transformation has a defined meaning in bacterial genetics 
> (it was the first proof that DNA is the genetic material) but 
> now means the introduction of plasmids into E. coli by  
> chemical or physical means.  
If you had read the original literature, the definition of transformation 
has always included the concept of introduction of DNA into the receptive 
recipient. There never was a proscription concerning the source or the nature
of the DNA. If you had read some more original literature, you would have
noticed that the process of Ca-dependent introduction of DNA into E coli was
originally studied with lambda as a tracer - and was described as 
transfection. When the generality of the process was demonstrated, the name 
was changed to transformation - since the result was a heritable alteration 
of the recipient bacteria.
To make matters worse, the same 
> process in eukaryotic cells is called transfection! This term was 
> originally reserved for the introduction of viral DNA into a 
> cell. 
If you had read the original literature, the process of introducing DNA into
a eukaryotic cell was studied with viral DNA as a tracer. Therefore the 
vocabulary is exactly correct. The fact that the process fails to
discriminate against nonviral DNA is no reason to rename the technique. Also,
if the technique is used to create cells with a heritable change, most 
individuals withwhom I have had contact use the vocabulary of transformation.
NO PROBLEM!!!!
 While it is too late to changes these terms, their use 
> leads to inaccurate communication and can produce sloppy 
> thinking.  These new processes should have new names to 
> distinguish them from their related genetic systems?  Are there 
> good alternate names for artificial plasmid transformation, 
> eukaryotic cell transfection, and cloning into phage vectors?
Maybe if you spent a little of your "net time" with any introductory genetics 
text while considering the subtle points of identity between superficially 
different events, we would be relieved of this burden to rename the wheel.
> Hank Seifert
> Northwestern University
> 



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