The basic three coat types show a consistent pattern of dominance:
wirehair - dominant over shorthair and longhair
shorthair - recessive to wirehair, dominant over longhair
longhair - recessive to wirehair and shorthair
Wirehair coats are usually double coats, they have a short, soft, dense undercoat and a coarse, straight, wiry topcoat or outer coat. The undercoat keeps the dog warm, with the density varying between breeds. The topcoat has a harsh appearance and stands slighty erect to protect the dog during adverse weather conditions, it is somewhat water repellent. Wirehair coats typically shed twice a year and require brushing, clipping or hand stripping to prevent mats. Clipping however has an adverse affect on the topcoat.
Shorthair coats show considerable variation in length, texture and density. Some shorthaired breeds always have undercoats, some breeds never do, and some individuals have an undercoat and others don't within a breed as well. Shorthaired dogs without an undercoat may shed a small amount year round or may follow a seasonal shedding pattern. Shorthaired breeds usually depend to some extent on an oily coat to repel water.
Longhair coats show the widest range of variety. Some breeds have long hair all over and only slightly shorter hair on the face and other breeds have a typical pattern of short hair in some areas and longer hair in others (short-face, leg fronts and feet, long-body and tail; etc.). Mode of inheritance is mostly unknown and the wide array of variance is possibly controlled by modifiers. Most longhair coats are double coats with a short, soft, dense undercoat and a coarse top coat. The undercoat is usually shed in the spring and the topcoat in the fall, however this is widely breed and individual variable as well as related in some extent to climate and seasons. Some longhaired breeds do not shed seasonally, they continually grow coat like humans, losing dead hairs only occasionally.
Unusual coat types include the wooly, corded and hairless. The wooly and corded coats have their own varieties and traits as well. The hairless coat can be dominant (Chinese Crested) or recessive (American Hairless Terrier) and each variety also has its own traits.
Coat quality traits have the widest possible range of features and the inheritance of traits such as density and texture appears to be inherited independently of basic type.
Density is affected by climate and coats become more dense (more hair per skin area) in colder weather. The variance of density is a hereditary trait and density was concluded to be a polygenic trait by Whitney, but a sparse coat was in general found to be dominant over a dense coat.
Texture is based between silky and coarse and Whitney in general, tentatively concluded that coarse is dominant over silky.
Undercoat is very variable between breeds and within the breed. Some breeds have no undercoat, some have an undercoat and in those with an undercoat some individuals will not have one. Some puppies are born with an undercoat and then lose it upon maturation. Undercoat is distinctly a herditary trait and having an undercoat appears to be recessive and lack of one dominant, again according to Whitney's research.
Wavy coats seem to be indeterminate in mode, but in general Whitney found straight coats tend to be dominant over wavy coats.
Kinky coats (Irish Water Spaniel) were concluded to be recessive to straight by Whitney.
Curly coats (Poodle) appear to be dominant to straight coats by Burns and Fraser's research.
Feathering on the backs of ears, legs and tails appears to be dominant over lack of feathering, according to Whitney.
Whorls or cowlicks appear to be recessive, but their location is variable, according to Pullig.