A quick look into the world of cats DNA analysis: those among us and those that we miss
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Our job here at Basepaws is to help you get to know your beloved felines on a molecular level and discover all the secrets hiding in their DNA. Our ultimate aim is to form a rich feline database to secure better health care for cats in the future, and fortunately many of you have already joined us on our mission!
Talking about DNA is super interesting, however, it often raises a lot of questions. What is DNA really, what does it look like, and where does it come from? What information does it carry? Why do I have to collect a DNA sample in this particular way? What if my cat passed away, but I still want to do a CatKit test? Today we bring you our guide to the science behind DNA analysis! Read on to learn more, understand better and find your way around the world of genetics a lot faster!
ABOUT FELINE DNA
What is DNA?
DNA, or deoxyribonucleic acid, is a complex organic molecule consisted from a double chain of connected nucleotides. Nucleotides are monomers built from three components: nitrogen-containing nucleobases, deoxyribose (sugar) and a phosphate group. There are four nitrogen-containing nucleobases that can be found in DNA: adenine (A), thymine (T), cytosine (C) and guanine (G). Adenine and guanine belong to the group of purines, while thymine and cytosine are pyrimidines.
Nucleotides are connected with each other in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next. This chain is called the polynucleotide strand. The covalent bonds between sugar and phosphate molecules form the phosphate backbone of the DNA helix.
DNA is built from two such polynucleotide strands. Two polynucleotide strands are joined together in a DNA molecule by hydrogen bonds between the nitrogen-containing bases. There are strict base pairing rules though. A purine base is always joined with the complementary pyrimidine base. I.e., adenine is always connected with thymine, and cytosine is always joined with guanine. Two polynucleotide strands joined in this way form a double helix – the DNA molecule (Figure 1).
Figure 1: The DNA consists from two polynucleotide chains. Each chain consists of nucleotides where sugar and phosphate molecules bond together. These bonds form the backbone of the DNA. Two polynucleotide chains are joined together by bonds between nitrogen bases. (source)
How is DNA organized?
A DNA molecule is surprisingly long. Feline genome (the complete genetic information of an organism) is about 2841.07 x 109 bp (base pairs) long. Therefore, the molecule has to be very tightly packed in order to fit in the nucleus of a cell. DNA molecules are packed into structures called chromosomes. Somatic cells carry two sets of chromosomes – one set inherited from each parent. Gametes (sperm or egg cells) contain only one set of chromosomes.
Cats have about 20,000 genes in their genome. All genes come in different variants. Different combinations of genes form different phenotypes (observable characteristics of an organism). Every kitten receives 19 chromosomes from each parent. Meaning it will have two variants of each gene – one from mom and one from dad. If the variants of a gene are the same, then the gene is considered homozygous and can only express the exact trait coded by that variant. If the variants of a gene are different, then the gene is heterozygous, and the phenotype will depend on the interaction between these two alleles. If one allele is dominant and the other one is recessive, then the dominant variant will be expressed in the phenotype. Likewise, codominant alleles will equally contribute to the formation of the trait.
In 2007, the genome sequencing of an Abyssinian cat named Cinnamon was finally completed and published. The draft of the feline genome led to the discovery of several cat genetic predispositions and the development of cat genetic fingerprinting.
WHY ANALYZE DNA?
DNA testing for humans and their pets has rapidly progressed in the last decade. DNA analysis is usually conducted for genetic predispositions, paternity and forensics.
Most pet owners are interested in knowing the breed of their furry family members. It can be super fun discovering a hidden ragdoll in your kitty or learning that your cat is 25% royal Siamese. Of course, we love our cats regardless of their breed, and yet many may wonder why we should analyze their DNA anyway?
"If animals could speak, the dog would be a blundering outspoken fellow; but the cat would have the rare grace of never saying a word too much" - Mark Twain
Cats are mysterious. Even if they could speak, they would probably choose not to. They would want us to prove our worthiness and would reveal their secrets on their own accord. This is exactly what we want to do with DNA analysis! Most of us don’t have records of our pets full family history. Owners whose cats exhibit signs of multiple breeds can now find out their true pedigree. Knowing the breed(s) of your cat will reveal certain genetic predispositions which it may be at a higher risk for. It may shed light on any unusual health or behavioral issues your cat may be already experiencing and allow you to know what to be on the lookout for in the future. We recommend sharing these results with your cat’s veterinarian who can then tailor treatment and/or future preventative care for your kitty. Getting to know your cat on a molecular level will help you do your best to provide them with the happiest and healthiest life.
SAMPLING THE DNA
To analyze DNA of any organism, one must acquire a suitable DNA sample. A suitable DNA sample is a sample that contains enough DNA that is not fragmented or contaminated.
Samples from known cats
Most commonly, DNA samples from known cats are collected by way of buccal swabs, plucked hairs and/or blood. The buccal swab is a way of collecting cells from the inside of the cat's cheek. This is a noninvasive method of collecting a sample that will (if sampled correctly) contain more than enough DNA for a full analysis. Blood sampling will also provide a good sample, but this method is considered invasive and isn’t used very often for these purposes.
Hair sampling is a commonly used method as well (Basepaws provides tools for this method in their CatKit test), but it does have its challenges. People usually assume that shedding hair is an ideal source for collecting the DNA needed for analysis. However, this is usually not the case. DNA can only be obtained from the hair follicle, not actual hair or fur. It is important to remember that DNA cannot be collected from cells whose life cycle is over and whose nucleus is already degraded (which is any hair that falls out/sheds naturally on its own). DNA is obtained from epithelial cells around the hair follicle. This means that if the hair fell out on its own, it is quite unlikely that there will be any DNA left suitable for analysis. Hairs pulled out directly from the animal will make a much more reliable source of DNA. This is because when hair is taken directly from the root, the epithelial cells from the follicle are still attached. This is crucial, which is why Basepaws asks its customers to obtain hair directly from their cats, and a fairly large amount of it too.
Sampling DNA from deceased pets
Basepaws gets a lot of inquiries about testing the DNA of deceased pets. When a family loses their cat, they often want to learn even more about their cat's genetics then when it was still alive to either get a new cat that will closely resemble their beloved one or to better understand their cat’s genetics for the betterment of their new cat's life. If the family decided to get a new cat with a personality, temperament or coat markings that closely resembled their deceased cat, then learning the specific breed(s) of their deceased cat would be step one. On the other hand, learning about the genetics of their deceased cat could give insight into what could have possibly been done differently to prolong its life.
So...is this even possible? In theory, yes. In practice, there are certain challenges to overcome. The samples are hard to obtain and there are several things to keep in mind.
1. Collecting saliva from deceased pets can be done but isn’t usually the most desired sample for testing for breeds.
2. Hair can be used, but again it is best if the hair can be pulled out directly from its root, while still on the animal. If the hair is collected from the furniture, toys or brushes, then it is important to remember that most of these hairs fell out naturally and therefore do not contain a lot of epithelial cells that contain enough DNA for the extraction and analysis. It may be possible to obtain enough DNA this way if the sample is big enough, but there is no guarantee.
3. Sometimes it is possible to obtain a tissue sample at a veterinarian’s office which can be sent to obtain DNA analysis.
Basepaws is currently working on developing a hair sampling method to target this particular group of pet owners who wish to purchase a CatKit for their dearly beloved.
Determining a cat’s breed
As mentioned above, most cat DNA tests aim to discover the familial history behind the pet which can be significantly beneficial for the improvement of its life.
After the DNA sample has been collected and sent back to the Basepaws, it is then extracted and analyzed in a lab. Analysts will first isolate the DNA from your sample and then they will run their tests and look for DNA markers that will reveal your cat’s pedigree. These analyses may take some time before the results are ready.
The DNA is a complex molecule that contains even more complex information. We hope we could help you get a better understanding of what DNA really is and how it has to be correctly sampled for a DNA test to be successfully conducted.