Genetics Part I: The Basics of Inheritance in Chinese Crested Dogs

Understanding a few basic principles of genetics makes it much easier to understand why the Chinese Crested breed has the traits and health considerations it does — from the hairless coat to inherited eye conditions. This is the first article in a series; part two covers how specific traits are calculated in practice.

Dominant vs. recessive traits

Every dog carries two copies of most genes, one from each parent. A dominant trait only needs one copy of the mutated gene to be expressed — this is the case for the hairless coat in Chinese Crested, governed by a mutation in the FOXI3 gene. A recessive trait needs two copies (one from each parent) to be expressed, which is the case for both primary lens luxation (PLL) and progressive retinal atrophy (PRA-rcd3) in this breed.

Carriers: the hidden middle ground

For recessive conditions, a dog with only one copy of a mutation is a carrier. Carriers are clinically normal — they show no symptoms — but can pass the mutation to roughly half their offspring. This is why pedigree research alone cannot reliably predict a dog's genetic health status; only DNA testing can.

Homozygous lethal genes

Some dominant genes are homozygous lethal: having two copies is incompatible with survival before birth. The Chinese Crested hairless gene is a textbook example. Because hairless dogs are heterozygous (Hh), pairing two hairless dogs (Hh × Hh) always produces a Punnett-square ratio that includes some HH embryos, which do not survive to term. This is a key reason breeders pair a hairless dog with a powderpuff dog (hh) rather than two hairless dogs.

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Continue to Genetics Part II: Defining and Calculating Traits for a closer look at how these principles apply to real breeding decisions, or see the health overview for the specific conditions mentioned here.