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Location: Scotland
Joined: Nov 2006
Posts: 254
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I can't comment on Bostons or Mals but Siberians are also affected by HC which can be late onset. HC in Siberians is known to be recesive so 2 dogs that pass their eye tests clear can still produce affected offspring if they are carriers.
2 carriers together will produce:
1 in 4 clear
1 in 4 affected
2 in 4 carriers
a carrier to a clear will produce
1 in 2 carriers
1 in 2 clear
no affected
clear to clear will only produce clear
affected to affected will only produce affected
until the marker gene has been identified, the only way to know if a dog is a carrier is if it produces an affected offspring.
Senile cateracts look different to HC and are not hereditary. I also know of dogs that were hand reared and developed nutritional cateracts, again not hereditary.
It is on the SSHC and SHCGB code of ethics that any dog failing it's eye test must not be bred from but siblings of affected dogs and known carriers can still be bred from (so not to reduce the gene pool) but all care must be taken to avoid breeding with other carriers.