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Recessive Gene Inheritance Patterns

Expected average results based on at least 16 puppies:
Both parents are NORMAL . . . not carrying the recessive gene. 100% of the offspring will be NORMAL.


Expected average results based on at least 16 puppies:
One parent is NORMAL; one parent is a CARRIER of the recessive gene . . . 50% of the offspring will be NORMAL and 50% will be CARRIERS. In PRA and RD, carriers can not be detected easily, thus pedigree analysis is critical.


Expected average results based on at least 16 puppies:
An AFFECTED parent will aslways produce CARRIER offspring. In this situation, only 50% will be AFFECTED but the other 50% will be CARRIERS. Affected individuals used for breeding automatically identify their offspring as CARRIERS.


Expected average results based on at least 16 puppies:
CARRIER to CARRIER breedings will produce 25% AFFECTED offspring, 25% NORMAL offspring, and 50% CARRIER offspring. In PRA and RD, the identification of the different offspring’s genetic make-up is extremely complex.


Expected average results based on at least 16 puppies:
An AFFECTED parent will produce only AFFECTED and CARRIER offspring. AFFECTED parent bred to a NORMAL parent will not produce any AFFECTED offspring, but all will be CARRIERS.


Expected average results based on at least 16 puppies:
An AFFECTED parent bred to another AFFECTED parent will always produce 100% AFFECTED offspring.


These are the only six possibilities of mating. Each of our dogs is the product of one of these six breeding combinations. Both PRA (Progressive Retinal Atrophy) and RD (Retinal Dysplasia) are accepted as recessive genes. This chart can be applied to the genetic inheritance pattern of both diseases.

 

Produced by the Genetics and Health Education Committee of the English Springer Spaniel Field Trial Association, Inc.