Expert: Dana Krempels, Ph.D. - 11/21/2007

Question
I recently read about the PEPCK-Cmus mice. In the article concerned it said that the genetic modification was achieved by injecting the gene of PEPCK-C enzyme into the embryo of the mouse. Is the general process of genetic engineering all that simple? What are the chances of the gene not binding as part of the overall code (do they have to be 'compatible' - able to bind as part of a similar or foreign strain)?

Answer
Dear Daniel,

No, the process of genetic engineering is not as simple as the article made it sound.  A gene to be inserted into a host organism is first inserted into an appropriate vector (a piece of DNA from a different species, usually a virus or bacteria) that will (hopefully) target the right area of the mouse genome where the gene is to be inserted.

There are three possible scenarios, post injection:

1.  No insertion of the gene
2.  ectopic insertion of the gene (i.e., in a spot you don't want it to insert)
3.  proper insertion of the gene (i.e., at the target location)

Published sources suggest that about 15% of the trials are successful, but as technology improves, so will this figure.  (It's from a textbook, Modern Genetic Analysis by Griffiths, so it's probably already out of date!)

The procedures used to insert genes into host organisms are various, and the appropriate technique varies with the host species and the genes in question.  It is far too complicated to explain in an email.  But if you are interested in learning more about it, the best place to start is with a general textbook in Genetics (and get a recent edition, since things in this field are changing so quickly!).  There are many very good authors, but if you'd like a recommendation, I'll be glad to help.

Hope this gets you started.

Happy holidays!

Dana