Siamese Colour Genetics Course · Lesson 7 of 8
Most Siamese have clear, solid points. A tabby point has barred legs, a striped tail and a neat “M” on the forehead — and the whole difference comes from a single gene switch. Siamese tabby point genetics sit on the agouti gene, which decides whether the points are laid down as solid colour or broken up into the ticked, striped pattern that gives us tabby (or, in North America, “lynx”) points. It’s the last pattern gene in the set, and one of the easiest to see once you know the markings.
In Lesson 6 we added red over the base colour. This lesson decides whether any of those colours appear as solid points or striped ones.
In this lesson
- What the agouti gene (A locus) does
- Why non-agouti gives solid points and agouti gives tabby points
- The markings that identify a tabby point
- Why every base colour can appear as a tabby point
- How solid and tabby pass down — and a common registration mix-up
The agouti gene — solid or striped
Pattern is set by the agouti gene at the A locus. The agouti version, A, is dominant and produces banded hairs — the ticked, striped tabby pattern. The non-agouti version, a, is recessive and produces solid, evenly coloured hairs.
Because non-agouti is recessive, a solid point needs two copies (a/a), and most Siamese are exactly that. A tabby (lynx) point has at least one agouti copy (A/A or A/a). This is the reverse of the recessive colours you’ve met so far: here it’s the pattern you can see everywhere — tabby — that is dominant, and the plain solid coat that is recessive.
The markings that give a tabby point away
On a pointed cat the tabby pattern shows up only where the colour is — on the points — which makes it easy to read once you know the signs:
- Barred legs — rings or bars rather than solid colour
- A ringed tail — banded along its length
- An “M” on the forehead — the classic tabby marking
- Pencilled “spectacles” — fine lines around the eyes and cheeks
- Spotted whisker pads and a dark-rimmed, pale-centred ear patch (the “thumbprint”)
One thing worth knowing, especially with young cats: even genetically solid (a/a) Siamese kittens often show faint “ghost” tabby barring in their first weeks, which fades as the solid coat comes in. A true tabby point keeps its markings for life; ghost markings on a kitten that later come good are not a tabby point. When in doubt, give it time and check the pedigree.
Every colour can be a tabby point
The agouti gene sits on top of everything from the earlier lessons, so it combines freely. Any base colour and any dilution can appear as a tabby point: seal tabby, blue tabby, chocolate tabby, lilac tabby, and so on — and, combined with the orange gene, even tortie-tabby (“torbie”) points. The agouti gene decides solid or striped; the other genes still decide the colour that’s being striped.
A note on the name
In the GCCF and across the UK, these are tabby points. In North America the same cats are usually called lynx points. Same genetics, different label — useful to know when you’re reading overseas pedigrees or breeder listings.
How it passes down — and a common mix-up
Because agouti is dominant, the inheritance runs the opposite way to the recessive colours:
- Two solid points (a/a × a/a) can only produce solid kittens — there’s no hidden agouti to surprise you.
- A tabby point can carry non-agouti (A/a) and produce solid kittens — so it’s the tabby, not the solid, that hides the alternative.
A quick worked example: a seal tabby point carrying solid (A/a) mated to a seal solid (a/a). Each kitten draws one A-locus allele from each parent — A + a gives a tabby, a + a gives a solid — so you’d expect roughly half tabby, half solid across the litter.
The mix-up to watch for: because faint ghost barring on solid kittens looks tabby-ish, and because a genuine tabby point’s colour name (“seal tabby point”) can be misread, tabby points are sometimes registered incorrectly — as a plain seal when they’re a seal tabby, or vice versa. If two solid parents “produce a tabby,” the far more likely explanation is that one parent was actually an under-marked tabby, not that agouti appeared from nowhere. Accurate records and a careful look at the markings keep the paperwork honest.
Key takeaways
- The agouti gene (A locus) decides solid versus tabby points.
- Agouti (A) is dominant and gives tabby (lynx) points; non-agouti (a/a) gives the solid points most Siamese have.
- Tabby points show barred legs, a ringed tail, an “M” and pencilled markings.
- Any base colour or dilution can appear as a tabby point.
- A tabby can carry solid, but two solids can’t hide a tabby — so a “surprise” tabby usually means a mis-marked parent.
That’s every gene in the set. In Lesson 8, the capstone, we put them all together and read a real pairing from start to finish — working out exactly which kittens a mating can produce, and in what proportions.
See the tabby point profile for how this looks in the coat.
