1. Dominant genes

2. Recessive genes

3. Hairless dog breeds
    Non-registered breeds 

4. Gallery

5. References

A hairless dog is a dog with a genetic disposition for hairlessness and hair loss. There are two known types of genetic hairlessness, a dominant and a recessive type.

Dominant genes

Dogs with dominant genes for hairlessness can pass their attributes to their offspring in natural conditions, that is, not under the control of humans. Therefore, it is possible that, in some parts of the world, groups of hairless dogs came into existence without human intervention. Later in history, people developed these groups into a recognized breed.

Worldwide recognized breeds at this time are the Chinese Crested Dog, the Xoloitzcuintli and the Peruvian Inca Orchid.

The Argentine Pila Dog and the Bolivian Hairless Dog are not registered hairless dog breeds.

Other breeds that were said to have existed in the past were the Abyssinian Sand Terrier (also known as the African Hairless Dog, Egyptian Hairless Dog and Elephant Dog, the last being a reference to its grey skin) and the Siamese Hairless Dog.{{citation needed|date=January 2013}}

This type of genetic structure is said to be homozygous pre-natal lethal for the dominant gene.^[1] This means that zygotes with two dominant genes cannot live. Therefore, all dominant-hairless dogs have a heterozygous gene structure. This allows a homozygous recessive type to persist, which is the coated variety.

For dogs where hairlessness is a dominant gene, hairless to hairless matings will on average produce 66.6% hairless and 33.3% coated puppies. For hairless to coated matings, there will be an average of 50%/50% coated to hairless ratio, while for coated to coated matings, all puppies will be coated^[2]

The Chinese Crested Dog's coated variety is called a "Powderpuff" and is a recognized type. The coated variety of Xoloitzcuintli (Mexican Hairless Dog) is recognized as a valid type for conformation showing with some registries, including the AKC.^[3] Coated varieties of the other breeds may or may not be recognized as valid varieties for conformation showing, depending on the breed and show or registry organization.

Recessive genes

The American Hairless Terrier (AHT) is the only dog breed with a recessive hairless gene. Unlike the hairlessness resulting from dominant genes, the AHT has no dental, skin or other health issues associated with the dominant gene hairless breeds. The only AHT distinguishing characteristics from its coated Rat Terrier foundation stock is its hairlessness. Other distinguishing features, such as colors and size, have been breeder-induced.

Hairless dog breeds

• Chinese Crested Dog
• Xoloitzcuintli
• Peruvian Inca Orchid
• Ecuadorian Hairless Dog (Perro calvo dorado ecuatoriano)
• American Hairless Terrier

Non-registered breeds

• Abyssinian Sand Terrier
• American Crested Sand Terrier
• Argentine Pila Dog
• Bolivian Hairless Dog (Hairless Khala)
• Jonangi Dog

Gallery

References

• Athletics at the 1999 All-Africa Games - Women's 200 metres
• Athletics at the 1999 All-Africa Games - Women's 400 metres
• Athletics at the 1999 All-Africa Games - Women's 400 metres hurdles
• Athletics at the 1999 All-Africa Games - Women's 5000 metres
• Athletics at the 1999 All-Africa Games - Women's 800 metres
• Athletics at the 1999 All-Africa Games - Women's discus throw
• Athletics at the 1999 All-Africa Games - Women's hammer throw
• Athletics at the 1999 All-Africa Games - Women's heptathlon
• Athletics at the 1999 All-Africa Games - Women's high jump
• Athletics at the 1999 All-Africa Games - Women's javelin throw
• Athletics at the 1999 All-Africa Games - Women's long jump
• Athletics at the 1999 All-Africa Games - Women's marathon
• Athletics at the 1999 All-Africa Games - Women's pole vault
• Athletics at the 1999 All-Africa Games - Women's shot put
• Athletics at the 1999 All-Africa Games - Women's triple jump
• Athletics at the 1999 Pan American Games - Men's 10,000 metres
• Athletics at the 1999 Pan American Games - Men's 100 metres
• Athletics at the 1999 Pan American Games - Men's 110 metres hurdles
• Athletics at the 1999 Pan American Games - Men's 1500 metres
• Athletics at the 1999 Pan American Games - Men's 200 metres
• Athletics at the 1999 Pan American Games - Men's 20 kilometres walk
• Athletics at the 1999 Pan American Games - Men's 400 metres
• Athletics at the 1999 Pan American Games - Men's 5000 metres
• Athletics at the 1999 Pan American Games - Men's 50 kilometres walk
• Athletics at the 1999 Pan American Games - Men's 800 metres