From: diannes@sonic.net   
      
   Rocky  <2dogs@rocky-dog.com> wrote:   
   >   
   > Dianne, what exactly are the genetics behind undescended   
   > testicles?  I've been have a disagreement with an acquaintance   
   > who wants to breed a crypto male - saying that it can be "bred   
   > out" in 3 generations.  The Padgett book I have doen't go into   
   > the genetics of cryptorchidism.   
      
   The genetics aren't precisely understood, and may vary by breed.   
   But generally speaking it seems to be inherited in a recessive   
   fashion, which is to say that neither parent needs to suffer from   
   the defect in order to produce it. (Well, obviously a bitch can't   
   suffer from an undescended testicle, but since some produce more   
   than others it is apparent that bitches can be carriers of the   
   trait.)   
      
   One of the more complete explanations I have is from the book   
   "Abnormalities of Companion Animals: Analysis of Heritability"   
   by C.W. Foley, J.F. Lasley & G.D. Osweiler (Iowa State University   
   Press, 1979). It states the following (I've added some explanatory   
   comments in square brackes[]):   
      
     "In dogs, most research reports suggest that the cryptorchid   
      state [that is, the state of having undescended testicle(s)]   
      is the result of a sex-limited [not expressed in females]   
      autosomal recessive gene [a gene that must be carried by both   
      parents]. Some reports indicate that cryptorchidism is not   
      controlled by a single gene but by possibly by two gene pairs.   
      The descent of each testicle would be controlled by one gene   
      pair. This theory would allow nine different genotypes, five   
      of which would allow for some form of cryptorchidism to be   
      expressed. Penetrance may also be low for this characteristic.   
      
     "The majority of veterinary practitioners have found little   
      success in trying to correct the cryptorchid condition with   
      hormone therapy. Unilateral [dogs with one undescended testicle]   
      or bilateral [dogs with two undescended testicles] cryptorchids   
      should not be used for breeding. If possible avoid the use of   
      dogs that have sired cryptorchids."   
      
   In short - unless there's some specific, well-documented variant   
   form of cryptorchidism that occurs in your friend's breed - your   
   friend is probably off-base. The nasty thing about recessives is   
   that they can travel along undetected for years and then pop up   
   again unexpectedly many generations later.   
      
   HTH,   
      
   Dianne   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)