Q.  What does a positive result mean?
A.  Testing positive for one or both of the HRD mutations means that your dog has one or two copies, in his/her DNA, of a dominant mutation which is responsible for Hereditary Renal Dysplasia.

Q. If it is a dominant gene, how come my dog is healthy?
A.  The mutation for HRD is a dominant with "incomplete penetrance".  This means that there must be other systems that in most cases can take over part or all of the functions of the normal gene in the development of the kidney.  Most animals with the mutation have only partial defects in the kidney, and will remain healthy for a normal lifespan. However, any animal which carries the mutation, even if it is itself healthy, can transmit the full-blown disease to it's offspring.  But since very few of the animals affected with the mutation actually have a serious degree of kidney malformation, most of the affected offspring will also be healthy, with only minor degrees of kidney defect.

Q.  What does the gene actually do?
A.  We know that the normal form of the gene is responsible for the normal development of the kidney.  The mutation somehow interrupts the normal maturation of parts of the kidney.  In most affected animals, enough of the kidney develops normally, that normal kidney function can be maintained.  But in some cases there is not enough normal kidney tissue to support life.

Q.  Should I use any "carriers" in my breeding program?
A:  If you have been breeding Lhasa apsos previous to testing, you have probably been breeding "carriers right along.  You have been basing your decisions on many factors to breed the best dogs you can.  the DNA test for HRD just gives you a little more information.