I'd never seen a pitbull/golden mix before!

Many dog species are specifically bred for deleterious physical traits.

Pugs experience respiratory distress, and increased intracranial pressure, because they’re selectively bred for the brachycephaly (the crushed-snout skull shape). Not because of inbreeding, per se. Inbreeding reduces the genetic mixing effect, which normally gives a small degree of protection to each offspring from the expression of recessive alleles. It doesn’t spontaneously generate defects, just causes them to be expressed slightly more often if the offspring’s genome was inherited from the pairing of two consanguine individuals who are part of a group where a certain recessive trait is more common that the general population. The pairing of either of those individuals with an individual from the general population is more likely to give the offspring a dominant allele to override the recessive one and not express the defect.

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