Genetics and the importance of not breeding from carriers 2008

It was my pleasure to be invited to speak to the proposed German Spitz Owners & Breeders Club seminar on Genetics. This  was held near Henley-in-Arden and the club’s hospitality and transport to and from Birmingham airport was first class. Although many of the issues that the German Spitz breed has ( and I refer here to Klein and Mittels collectively) are not too dissimilar similar to TTs, it is always a great learning experience to find out about other breeds and how they are tackling issues.

I obviously discussed colour inheritance largely to illustrate complex multi-factorial (polygenic) inheritance i.e. one characteristic controlled by several genes, each of which has a different number of alternative alleles, and which interact with one another. There is a multitude of colours in this breed, all being allowed. So there are chocolates (sometimes called browns in German Spitz) and chocolate & white particolours, and dilute chocolate (gold and creams), sables with black tips, sables with chocolate tips, black & tans, chocolate & tans, black ticked, chocolate ticked, and how about this one: lilacs. Only the breeders could tell me what colour this is and they said it is like a Weimaraner or an Isabella fawn Dobermann. So it is likely to be a dilute chocolate with the final lilac hue caused by either the chinchilla allele or the intensity allele, or another modifier.

Retinal Dysplasia (RD) is the breed’s big concern. Although data about the condition is sparse in this breed the over-whelming evidence in other breeds is that it is a simple autosomal recessive mode of inheritance, so we discussed the implications of that and of breeding from known carriers and relatives of carriers.

Breeders told me that it seems to be congenital (present at birth or shortly afterwards) and although clear diagnoses are possible when eyes are examined at a very early age of around seven weeks, if the condition is present it can be diagnosed with certainly from around four months of age. This provides a ray of hope because diagnosis can be made before breeding age. However if a DNA test can be found then it should, if breeders are responsible, avoiding the mating of the parental carriers that will produce cases.

Mike Tempest