Henley's DNA results & my thoughts so far...
Henley is heterozygous for polydactyl (Hw/N), which means approximately 50% of his kids will also possess the polydactyl trait and also pass this trait on. The following shows the 3 variants for the polydactyl allele which is dominant over non-polydactyl:
Hw/Hw = Homozygous for polydactyl, every single baby produced will possess the polydactyl trait, and in turn past this trait down
Hw/N = Heterozygous for polydactyl, carries both poly & non-poly alleles, and 50% chance of kittens possessing this trait
N/N = does not carry the polydactyl allele, will not possess the trait or pass it down
Note: I have been given the impression by my US breeder that the notion of breeding poly x poly is questionable, particularly in Euro breeders. I would be very interested to find out more opinions of this. My breeder's opinion is that it is quite safe under the right circumstances. Here is the short explanation: Apparently it is widely thought that pairing two polys together is dangerous, this is because it is generally noted that with genetic mutations if you pair or duplicate it, this in turn, enhances it - and this goes for good or bad traits. There have been several studies (not recent unfortunately) which tend to actually show that pairing two polys together is not harmful. It obviously creates a homozygous line (100% of polys will be passed to offspring), but apparently in general, it doesn't appear to create any deformities. There is an exception to this... the "messy beast" article (referenced in my polydactyl blog post) says there is a "bad" form of the mutation which is associated with a disorder known as a "twisty cat", or scientifically known as radial hypoplasia. This condition is SERIOUS and should be avoided at all costs. Genetic defects/mutations cannot be "diluted", they are either there or not. So the best way to prevent this, is to avoid breeding any cats that have this deformity, and it's as simple as that. Hence why all my polydactyls will be xrayed from the shoulder/hip joints down to their toes to physically clear them from any deformity. It is expensive, but worth it in my opinion to keep these cats healthy.
Tabby vs solid coat colour
The second main trait that I was very interested in is the agouti (tabby) vs solid coat type. The agouti allele is dominant over the solid coat colour (non-agouti). It only takes one copy of the allele to be displayed as a phenotype. Henley is heterozygous (A/a) for this gene and carries both solid and agouti alleles. I am so happy about this! It is displayed as follows:
A/A = homozygous agouti, will display tabby pattern and will ONLY pass down agouti pattern
A/a = heterozygous agouti, most probably displays agouti pattern, can pass down both the agouti pattern AND non-agouti (solid) coat colour
a/a = homozygous for non-agouti (solid), will only pass down the solid coat colour
I am always intrigued about the dilute gene. With felines, their colour starts out black (red is the second primary colour but is not always present, it is an additional gene that is sex-linked and has it's own expression - I may go into this later, but it is still confusing for me!). Henley produces homozygous black pigment (displayed as B/B). Black dilutes to blue and red dilutes to cream (or cameo, as known in the US). Dilute is an autosomal recessive trait, which means it requires two copies of the allele to display the phenotype. Either one copy from each parent, or two copies from one parent. Henley's coat colour is not diluted (it's black rather than blue) so I was very interested in what his genotype would be. Seeing as his mother is a blue mackerel tabby, she should carry both dilute alleles (d/d, ie. she is homozygous for dilute). In turn, she should then pass at least one copy to her offspring. Henley's father does not carry dilute at all. So theoretically, Henley should be heterozygous for dilute, he would have received at least one copy of the dilute allele from his mother, though you cannot see this in his phenotype as he is a black-silver (rather than a blue) Alternatively, if Henley displayed the blue dilute colour, he would have received both copies from his mother. Henley's DNA profile indeed confirms that he is heterozygous for dilute (D/d), and this was exactly the result that I was expecting and hoping for. Overall, this is expressed as follows:
D/D = homozygous dark coloured, will never pass dilution to their offspring
D/d = heterozygous for dark coloured, will not display the dilute colouring but can pass dilution to their kitten
d/d = homozygous for dilute colouing, all kittens be passed dilution colouring (kittens may or may not display colouring, and may be homozygous or heterozygous)
An additional note: Black is the starting base colour, Brown is a variant (mutation) of the Black gene, and Blue occurs when the Dilute gene is present.
The silver shaded colouring is expressed by the Inhibitor Gene. This gene suppresses the pigmentation of the hair shaft. It is a dominant gene which only needs one copy of the allele to show in the phenotype. Henley is clearly silver-shaded. The gene is expressed as follows:
I/I = homozygous inhibitor, cat will display the phenotype and all offspring will possess this trait also
I/i = heterozygous inhibitor, the cat will probably display the phenotype, and will produce both solid and silver kittens
i/i = homozygous for being "without white undercoat", all solid cats posses this allele combination
Additional note: Some people claim that silver and smoke are from different genes. This is debatable. More commonly, it is accepted that a "smoke" colour can ONLY occur on a non-agouti cat (solid colour), whilst a "silver-shade" occurs with an agouti pattern (tabby).
Maine Coon disorders/diseases
As expected, Henley is clear for ALL of the known maine coon disorders:
HCM - Hypertrophic cardiomyopathy
SMA - spinal muscular atrophy
PKdef - pyruvate kinase deficience
Factor XII Deficiency - blood disorder
You can see the rest of the disease/disorder traits in his full DNA profile, which he is also clear for.
There are HEAPS of online sites that talk about feline genetics. One that I found quite simple and clear was this page by EuroCatFancy:
Eurocatfancy: Genetic Terms in Cats
- - - - -
1 .These blog posts will likely be developed and added to over time as I learn more information.
2. While some breeding "secrets" are kept as unwritten law, the general concept of what I write here is freely available to find if you look in the right places. The feline associations (Australian/American/European) are a good place to start. The PawPeds website also has some interesting information (not always/strictly scientific though).
3. Some really really important questions for anyone to ask themselves when embarking on new or controversial scientific adventures are:
a) Why am I getting angry about someone pursuing a certain line/trait?
b) Is it because it's scientifically or genetically unsound?
c) Is it unethical?
d) Is it because someone simply "told me it's wrong/right"?
e) Is it fear of the unknown?
4. Be brave. Be courageous. Explore something new.
5. Admit your mistakes and learn from them.
6. Please don't blindly believe me. Also, please don't blindly hate on me if you have no scientific backing.
7. Ask your own questions, and seriously, genuinely, seek answers. Make informed decisions.
8. Lastly, as always, be kind.