Coat: The Labrador Retriever's coat should be short and dense, but not wiry. The coat is water-resistant, so the dog does not get cold when taking to water in the winter. Occasionally, Labradors will exhibit small amounts of white fur on their chest, paws, or tail, and rarely a purebred Lab will exhibit brindling stripes or tan points similar to a Rottweiler. These markings are a disqualification for show dogs but do not have any bearing on the dog's temperament or ability to be a good working or pet dog. Puppies of all colours can potentially occur in the same litter. Colour is determined primarily by three genes. Variations in numerous other genes control the subtler details of the coat's colouration, which in yellow Labradors varies from white to light gold to a fox red. Chocolate and black Labradors' noses will match the coat colour.