Complex sentence: A fifth includes tabby as part of another basic color pattern, the "patched" tabby, which is a calico or tortoiseshell cat with tabby patches (the latter is sometimes called a "torbie").
Split into simpler sentences: A fifth includes tabby as part of another basic color pattern. The "patched" tabby is a calico or tortoiseshell cat with tabby patches (the latter is sometimes called a "torbie").