Congenital short bowel syndrome.
As well as selecting animals for physical traits, it is important to select them for health traits as the prevalence of Polycystic Kidney Disease in Persians and Exotics demonstrates.
In nature, inbred individuals tend not to survive; this removes harmful mutations from the population.
Chromosomes carry genes.
Mutations in filamin 1 prevent migration of cerebral cortical neurons in human periventricular heterotopia.
The video below walks through linkage as a violation of independent assortment and explains how crossing over breaks linkage.