DNA tests for inherited diseases in cats
Autosomal recessive genetic disorders in cats
Many genetic DNA diseases in cats are inherited as autosomal recessive disorders. Two copies of the mutant DNA are needed for the disease to develop. With one copy of the mutation, the cat is a carrier and can pass it on to its offspring, even though it is healthy. Such a cat can be safely mated to a completely healthy cat. About half or 50% of kittens are expected to have this gene mutation and will become carriers. Considering this fact, it is recommended to test the cats before further mating.
When mating two cats that carry the gene mutation, 25% of the offspring will have two mutant alleles, which will result in the manifestation of the disease during their lifetime. Therefore, mating is not recommended in this case.
If a cat has mutations in both alleles of the gene, it will pass this mutation on to all (100%) of its offspring.
Interpretation of results
DNA tests for inherited diseases will most often show alleles of the tested gene and the related changes:
- there are no mutations in any allele (no mutation homozygous) - the cat is healthy;
- the mutation is in one of the alleles (the changes are heterozygous) - the cat is a carrier; there may be minor changes in health along with mutations that cause some diseases, such as reduced level of enzymes, or the disease may be mild. The mutation will be passed on to 50% of the offspring;
- the mutation is in both of the gene alleles (the changes are homozygous) - the cat is sick, the mutation will be passed on to all its offspring.
Autosomal dominant and co-dominant genetic disorders in cats
Diseases that are inherited in an autosomal dominant manner are manifested even if the cat has inherited only one copy of the mutant DNA. All cats with the mutant allele (whether in one or both) are ill or may have some symptoms or mild illness. It is not recommended to mate such cats, as 50% or 100% of the kittens will be sick (depending on whether the sick cat is mated with a healthy cat or sick cats with each other, or a cat with two mutant alleles). Also, kittens who presumably contain at least one copy of the mutant DNA should be tested before further mating.
Co-dominant heredity means that in a cat with one defective gene allele, the disease may be partial, only present some features, or may be mild.
Interpretation of results
The interpretation of the results of autosomal dominant and co-dominant inherited DNA disorder testing will also show the alleles of the tested gene and the related changes:
- there are no mutations in any allele (no mutation homozygous) - the cat is healthy, the mutation cannot be passed on to offspring;
- the mutation is in one of the alleles (the changes are heterozygous) - the cat will be ill, the disease may be partial or mild (co-dominant), or there is an increased risk of developing the disease during the animal’s lifetime. The mutation can be passed on to half (50%) of kittens;
- the mutation is present in both of the gene’s alleles (the changes are homozygous) - the cat is ill or very likely to develop the disease. The mutation will be passed on to all offspring.