The scientist would compare the symptoms of that animal to animals with different mutations in the same gene.
Genetic studies depend on successfully mating animals and producing offspring.
This means that mutations that cause the animal to die or to be sterile can cause serious trouble for the scientist. As long as these types of mutations are recessive , lines of animals carrying the mutations can be propagated and used in experiments. When someone speaks of Human Genetics , they mean the study of the DNA fragments that comprise human genes. In the last 15 years, scientists have shown that the genes of animals as varied as bacteria and mammals have a very high degree of similarity, not only in DNA sequence, but in the functions performed by the homologous genes. This amazing similarity in the genetics of all organisms means that studying the genetics of model organisms such as fruit flies or zebrafish can tell a scientist a great deal about the human equivalent of these genes.