[Chronometer]

Firstly, I'd like to apologise for the hideous cover. If it's too ugly and burns your eyes, I'll fix it as soon as possible c:

Secondly, I hope this is the correct forum for a thing like this. It doesn't quite fit anywhere else. Mods, if I've done something wrong, please move this to an appropriate topic!

Thirdly, I would like to emphasise the fact that I am in no way an equine genetics expert. I just happen to enjoy the topic and think it would be nice to share with anyone else interested in horses/genetics. This may also be somewhat useful for all the equine adoptables I see around CS c:

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With that out the way, I assume you're here to learn about colour genetics! This is a fascinating topic, though just like algebra, I doubt it will be useful in your everyday life. I'm a student, and I like to use big fancy words like 'homozygous' because they make me feel smart. Sounds like a foreign language, no? Thank goodness I have a handy explanation sheet of all the technical speak before I even get onto coat colors.

The gene we will be using for these fun examples is Tobiano, a common white pattern found in horses. It will be denoted by the abbreviation uppercase T for a dominant gene and lowercase t for a recessive gene. Ready?


Homozygous Dominant~ Eg: TT
The horse carries only one (hence the -homo bit) type of the gene; the dominant type. The horse will display characteristics of the Tobiano pattern. One of these copies will be passed down on to offspring regardless of the mate's genetic status, ie the foal will always end up with one copy of dominant Tobiano, T plus either a recessive or dominant copy from the partner. The foal may be TT or Tt

Heterozygous Dominant~ Eg: Tt
The horse caries two (hence the -hetero) types of the gene; One dominant T, and one recessive t. It will still look like an Tobiano horse, since the dominant gene is there to bully the little lowercase letter and get what it wants. However, when breeding, things will be different from a TT horse. Your Tt horse may pass on its T, in which case the foal will have one dominant copy, and therefore will be a Tobiano. The horse may then instead pass on its t, the recessive gene. If this happens, then the foal will not display Tobiano unless it receives a dominant copy of the pattern from the other parent (who must have one or two dominant T genes).

Heterozygous Dominant (Again)~ Eg: nT
Hold on Chrono, you added an 'n'! What!?
This is the exact same as Tt. This literally translates as one T, just like Tt. It just cleans things up to remove the recessive gene and ad the n sometimes. It may have some special meaning, but I honesty don't know why some people use this way of writing heterozygous dominant. Try to avoid this until you are comfortable with genetic codes c:

Recessive~ Eg: tt
This horse does not carry any dominant Tobiano genes, and therefore does not display the pattern. His foals will always receive one copy of the recessive gene, t. In other words, this horse can never have homozygous Tobiano foals.


Here's a handy little chart to think about when breeding horses with the Tobiano pattern.


TT x TT Homozygous Dominant x Homozygous Dominant
100% chance of a TT foal. Both parents contribute one dominant T gene.
This foal will display the Tobiano pattern

TT x Tt Homozygous Dominant x Heterozygous Dominant
50% chance of a TT foal, one dominant T from each parent.
This foal will display the Tobiano pattern
50% chance of a Tt foal, on dominant T from one parent, and one recessive t from the other.
This foal will display the Tobiano pattern

TT x tt Homozygous Dominant x Recessive
100% chance of a Tt foal. One dominant T from one parent, and the recessive t from the other.
This foal will display the Tobiano pattern

Tt x Tt Heterozygous Dominant x Heterozygous Dominant
50% chance of a TT foal, one dominant T from each parent.
This foal will display the Tobiano pattern
25% chance of a Tt foal, one dominant T from one parent, and a recessive t from the other.
This foal will display the Tobiano pattern
25% chance of a tt foal, two recessives t from the parents.
This foal will not display the Tobiano pattern

Tt x tt Heterozygous Dominant x Recessive
50% chance of a Tt foal. One dominant T from one parent, and the recessive t from the other.
This foal will display the Tobiano pattern
50% chance of an tt foal. Two recessives t from the parents.
This foal will not display the Tobiano pattern

tt x tt Recessive x Recessive
100% chance of an tt foal. There are no dominant genes in this pairing to pass on, only recessive ts.
This foal will not display the Tobiano pattern


Sorta stolen from an explanation to the great Freedom! Hope you don't mind <3
Take a deep breath. Count to ten slowly. Remind yourself that Chrono is the equine colour genetics overlord and must be worshiped by sacrifices of chocolate. Now, if you don't want to memorise a chart like that, an easy way to calculate
the genetic outcome of a pairing is a Punnet Square. Here is a handy guide on how to use one. Replace the letters on
the top and down the left side with a set of Tobiano zygosities to practise.

I'm going to revise this chart and definition bit and replace the Tobiano with the Dun dilution since I'm definitely going to confuse people when I talk about linkage and KIT mutations like Tobiano.

Fancy Words & Definitions


~Allele
One of two genes that can occur at one special spot (locus) of a chromosome. Alleles on the same locus control the same trait.

~Chromosome
A teeny structure in a cell that contains genetic information as DNA (deoxyribonucleic acid). Chromosomes come in pairs - one from mum and one from dad. Horses have a grand total of 64 chromosomes (32 pairs).

~Dilution
Dilution genes are fun and crazy things which affect the animal's base colour. They tend to lighten and change the base colours just because they can.

~Gene
A segment of DNA which is on a specific locus of a chromosome. It controls inheritable characteristics like eye colour.

~Genotype
The genetic makeup of an organism. People like to call genetic codes genos, eg EE/Aa/nCr/DD/nO/nT/nLp

~Locus
The specific location of a gene on a chromosome.

~Phenotype
The result of an expression of a genotype; what you see like hair colour or eye colour eg Dunskin Frame Overo Tobiano Appaloosa


Navigation

Intro:
~The Basic Base Colours
Extension and agouti

Dilutions:
~Cream & Pearl
MATP and its shenanigans

~Champagne
Shiny horsies

~The Dun Dilution
Primitive ponies are pretty c:

~Silver
Yes, it's a dilution.

White Patterns:
~KIT Mutations
Tobiano
Roan
Sabino
White Spotting

~Frame Overo
Don't just call it 'overo'

~Splashed White
Panted horses

~Rabicano
Not to be confused with true roan

~The Leopard Complex
Spots, spots, and more spots

Modifiers:

Markings:
~Leg White
Them reiners call it 'chrome'

~Facial White
Time to crack out the sun cream and UV masks

~'Bend-Or' Spot'
Spots

~'Birdcatcher' Spots
More spots

~'Chubari' Spots
Even more spots

Random/Unexplained:
~Brindle
Stripesss

~Somatic Mutations
When stuff doesn't work

~Chimeras
When stuff really doesn't work

~Macchiato
Dilution and pattern?

~Manchado
Everything's better in South America

~Gulastra Plume
Mind-boggling

~Mushroom
Dull grey and boring

~''Honey'
These darn Morgans

'Light Black'
What colour is this horse?
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Feel free to post and mark. This is a massive and ongoing WIP