Understanding SFA Color Inheritance and Geneticsa guide to the world of offspring color probability
These are the genetic codes according to the world of SFA and are not perfect matches to their irl counterparts in real gene tests for the sake of simplicity and clarity for our artists and members.
The Base Genes------------------------------------
Extension: E
Agouti:A
Brown: At
The Modifiers------------------------------------
Cream: C
Dun: D
Silver: Z
Champagne: Ch
Flaxen: f
Grey: G
Roan: Rn
The Paint Genes------------------------------------
Tobiano: To
Overo: O
Splash: Spl
Sabino: Sa
Tovero: To + O
Manchado: ma
this is a rough guide to using Punnett squares, calculating offspring colors, and understanding combinations of different genes. Like the last post, some of these are simplified to fit lore and to benefit the artist and members.
About Heterozygous and Homozygous---------------
Heterozygous: In which the two alleles of the gene are not the same, one is dominant and one is not, meaning the horse has a 50% chance to pass the gene to offspring.
Homozygous: In which the two alleles of the gene are the same, both are either dominant or both are recessive, either way the horse has a 100% chance of passing a copy if both are dominant.
Dominant vs Recessive Presenting---------------
Dominant Presenting: one or more
dominant alleles is needed to present this gene. "EE" or "Ee" would present black, but ''ee" would not.
Recessive Presenting: flaxen and manchado are the only two SFA genes that require two
recessive alleles to present. A horse with Ff or FF would not present flaxen but ff would. Chestnut can be presented with "ee/aa" in addition to one or mroe copies of agouti but anything bay or bay based
requires at least one copy of agouti.
Using Punnett Squares---------------
Calculator LinkUC Davis CalculatorTaking the mare and stallion's genos and entering them into Punnett squares is your best bet and identifying possible coat colors for the foal. Running fewer genes at a time and taking probability is recommended. As mentioned however, there are some reasons why you wouldn't need to put genos in a Punnett square to know what your going to get, thinking back to the heterozygous vs homozygous if you have
two homozygous carriers OR a heterozygous and a homozygous carrier you will be guaranteed the presentation of that gene except in the case of flaxen or manchado.
It is good to note that the only time a horse CANNOT be homozygous for a gene is in the case of
overo (O) as that tends to cause "lethal white" and offspring do not tend to survive this. SFA bans the breeding of two horses carrying overo for this reason.
What Cannot Be Inherited?---------------
In short, anything that doesn't have a listed genetic code to it. Markings, specialty coats, shades of any specific color (ex. cherry bay vs dark bay), or pinto spot shapes. Just because you have two solid black parents doesn't guarantee you a solid black foal, all markings are rolled for randomly. As tempting as it would be to let chimera or bleach pass, they are specifically reserved for certain numbers thus these special markings and colors cannot be genetically passed down. If you have a specific marking set for a specific coat in mind, its best to purchase a "custom horse ticket" for that.
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