no mutation is the appearance of a new or non normal allele value of a gene variable i said or non normal because some apparently appear repeatedly e g it is generally thought that the uk's queen victoria did not inherit the hemophilia allele from either parent but it appeared spontaneously in her and spread throughout the royal families of europe by intermarriage dog breeding is artificial selection by deliberate human action and works by increasing the frequencies of the desired alleles in the breeding group and or by eliminating undesired alleles but dog breeders don't think in terms of genes only of desirable undesirable traits hope that helps re mutations' sound to the layman rather dramatic that's a fair point which the article should clear up generally the more dramatic mutations will be unviable and in placentals mammals including humans will usually be spontaneously aborted can't remember the incidence of this in humans but it's surprisingly high most mothers are unaware of it because such embryos usually abort before symptoms of pregnancy appear viable mutations are rare and small which is why evolution is so slow by human standards