Hello all!
For this lesson we'll be discussing tabbies. This a bit more complicated than the others, because there are several genes all at play. Let's start with what a tabby is. The official term for a tabby is "agouti." This basically determines whether an animal is agouti or solid. An agouti animal, which is considered a natural coloration, has banding in their fur. This means that some parts of the hair are dark and others are light. Agouti is often the color of many wild animals, as the differing coloration tends to offer better camouflage. The agouti locii is as follows:
| Genotype | Phenotype |
| AA | Agouti |
| Aa | Agouti |
| aa | Solid |
The agouti gene alters coloration to be:
| Solid | Tabby |
| Black | Brown tabby |
| Blue | Blue tabby |
| Chocolate | Chocolate tabby |
| Lilac | Lilac tabby |
| Cinnamon | Cinnamon tabby |
| Fawn | Fawn tabby |
Mmasy, Bruno (July 3, 2011)
Now I previously mentioned that there were several genes all acting together to create a tabby. That very first one determines whether we have a tabby or not. The next three genes determine what kind of tabby we have.
| Genotype | Phenotype |
| TaTa | Ticked tabby |
| Tata | Ticked tabby |
| tata | Non-ticked (Mackeral or Spotted or Classic) |
| Genotype | Phenotype |
| SpSp | Spotted tabby |
| Spsp | Spotted tabby |
| spsp | Non-spotted (Mackeral or Classic) |
| Genotype | Phenotype |
| McMc | Mackeral tabby |
| Mcmc | Mackeral tabby |
| mcmc | Classic tabby |
Okay so let's make sense of these tables. After determining that we do have the agouti gene, we turn toward the tabby modifiers. Ticked tabby masks over Mackeral, Classic and Spotted. Ticked must be off, or recessive, in order to get any of the others. In that same sense, Spotted must be off, or recessive, to get Mackeral and Classic. Spotted is masked by Ticked, but Ticked is not masked by Spotted. Classic is recessive to Mackeral. So the tabby modifiers go Ticked -> Spotted -> Mackeral -> Classic. This means that each gene is special, meaning they can carry various tabbies. For example, let's say they are Spotted but a heterzygous for it (Spsp). This means that it does not have Ticked so we know they are tata. We'll say they have Classic tabby too, so that's mcmc. And they match up with a Ticked tabby that is heterozygous (Tata). Because they are Ticked, we know they are masking everything so we'll say they are heterozygous for Spotted and homozygous for Mackeral.
| ta Sp mc | ta sp mc | |
| Ta Sp Mc | Tata SpSp Mcmc | Tata Spsp Mcmc |
| ta sp Mc | tata Spsp Mcmc | tata spsp Mcmc |
Notice how I put all the genes together in one row? That means that you can combine all the genes in one punnet square. It's much simpler to do it this way but feel free to do them individually if it confuses you. So our outcomes for this are Tata SpSp Mcmc (Ticked tabby), Tata Spsp Mcmc (Ticked tabby), tata Spsp Mcmc (Spotted tabby) and tata spsps Mcmc (Mackeral tabby). That means we'll have a 50% chance of a Ticked tabby, 25% of a Spotted and 25% of a Mackeral.