1. Homozygous healthy:
Genotype female: N(X)/N(X),
Genotype male: N(X)/Y (homozygous healthy)
A dog like this is healthy and does not carry the mutated x-chromosome. Offspring of this dog will
not get the mutated x-chromosome.
2. Heterozygous carrier (only female):
Genotype female: N(X)/FIX(X) (heterozygous carrier)
A bitch like this carries one copy of the mutated gene. It is unlikely that the bitch will suffer from
haemophilia B, however there is a 50% chance that she will pass on the mutation to her offspring.
3. Homozygous affected:
Genotype female FIX(X)/FIX(X) (homozygous affected)
Genotype male FIX(X)/Y (hemizygous affected)
Because of the x-chromosomal mode of inheritance, a homozygous affected female dog carries
two mutated x-chromosomes and a homozygous affected male dog carries one mutated
x-chromosome. Female and male homozygous affected dogs have a high risk to express
haemophilia B. The bitch will pass on the mutation to a 100% of her offspring and 50% of
the offspring of the male dog will get the mutated x-chromosome.