In one sentence, describe what the following article is about:

In general, Purebred Cavaliers have predictable traits. If you purchase a Purebred Cavalier, you can expect them to be energetic, lovable house pets with fairly manageable coats. Genetically speaking, Cavaliers have a happy-go-lucky predisposition. If you purchase a Purebred, you can expect such a temperament. Non-Purebred Cavaliers may adopt some of the biological traits of whatever other breed they are mixed with. If they are mixed with a hound, they may have a stronger instinct to hunt and bark. Similarly, if they are bred with low-energy dogs like shih tzu, they may lose that energetic luster that made you fall in love with them in the first place. People covet pure-bred Cavaliers. This means that they have been bred from a limited gene pool. In order to be designated a pure-bred, many places inbreed their dogs, and others unwittingly breed from a gene pool that is too small. This has very real and extremely unfortunate consequences. Pure-bred Cavaliers run a high risk of suffering from heart disease, disc disease, and/or a severe neurological issues.   Heart disease: In the UK, 59% of Cavaliers over the age of 4 years old have a heart murmur. At nearly two-thirds of the UK's population of Cavaliers, this is an extraordinary statistic.  Chiari malformation and Syringomyelia: Basically, this condition means the dog's skull is too small for its brain. This causes dreadful nerve pain. The veterinary textbook "Breed Predispositions to Disease in the Dogs and Cats" lists this condition as "very common" with signs developing between 5 months to 3 years of age.   Epilepsy: Dogs may develop seizures at any time, but between 6 months to 6 years is the most common time   Disc disease:  This is another "common" condition, especially as Cavaliers age.  Most of the time, you won't know that your Cavalier is prone to slip discs, until you see it walking stiffly or reluctantly lowering its head to its food or water bowl.
Consider the pros of selecting a Purebred Cavalier. Assess the drawbacks of getting a mixed breed. Consider common Cavalier health issues.