Jumping genes?

Beverly Erlebacher bae at cs.toronto.edu
Fri Sep 18 16:03:45 EST 1998

In article <36029B5F.3D8D at hem2.passagen.se>,
Svante Karlsson  <svantek at hem2.passagen.se> wrote:
>Can segments of DNA "jump" between species creating mutation? The
>following has come to my ears: A couple of years ago scientists did
>genetic engineering on the DNA of a crop to make it resistant to some
>form of a weed controlling. After some time they discovered that the
>weed suddenly also was resistant to the same weed control. From that
>they concluded that pieces of DNA must have "jumped" from the crop to
>the weed.
>   To me this seem rather fantastic. The source is a friend of mine.
>Some years ago he had a girlfriend studying genetics at Frie Universität
>of Berlin who told him this.
>  If anybody knows anything in this issue please let me know even if
>it's just to say that the scientists have found a plausible solution to
>problem without referring to jumping genes.

While viruses could carry bits of DNA between different species of host
plant, remember that crop plants may have related species growing as 
weeds among them.  In the incident I read about, herbicide resistance 
was carried from rapeseed or a similar crop to wild mustard.  While natural
crosses between different but related species are probably uncommon, there
are a lot of plants in a field and herbicide application is a very strong
selector for resistance.  So if a cross of the crop and weed shows herbicide
resistance, it won't take many generations of the weed before all will be
resistant.  Plants often succeed as weeds by having short generation times 
and lots of offspring.

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