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Spotted Genetics

What will I get?

This is one of the most frequently asked questions, "what will I get coat colour-wise, if I put my mare to Jason?"  There are many different factors that contribute to the inheritance of a spotted coat pattern.

There is no guarantee of coat pattern when crossing two spotted horses; it can result in solid coloured as well as spotted foals; just as a spotted and a solid horse very often produce a spotted foal when bred to one another. 

 

If a foal appears to have been born solid, the characteristics above may start to appear (or be present) and may indicate that the horse/pony will 'colour out', and gain more spotted patterning, as it gets older.

Hopefully this page will go some way to explaining the basics of spotty genetics.

Weatheroak Georgina and Weatheroak Manor King Solomon

Lp gene - Leopard Complex

Leopard complex spotting (LP) is found in several breeds of horse and is characterized by the absence of pigment (white spotting) in the coat, and associated pigmentation characteristics (Bellone et al., 2013).  It's discovery in 2013 was ground-breaking in the world of spotted breeding, as it gave breeders another 'tool' with which to make educated choices, when choosing a mate for their mare.

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Pattern Modifiers

There is no PATN2 gene that codes for blankets.  Rather, it is thought that the differing degrees of patterning 0-70%, are due to inheritance (or otherwise) of many different pattern modifiers.  These form a cumulative effect, so if more are inherited, the louder the patterning.

Trintiyhouse Top Draw Knabstrupper Mare.jpg

The Appaloosa Project

The Appaloosa Project is the ultimate source for people who want information on appaloosa coat colouring - it is the same genetics for all the spotted equine breeds - Appaloosa, Knabstrupper, British Spotted Pony etc.   The site/group is run be researchers, but talks plain english with great diagrams

Appaloosa Project.jpg

PATN1 gene - the first 'pattern' gene to be identified

LP determines if a horse will have a leopard complex spotting pattern while other genes determine the extent (or amount) of white patterning present. One of these genes has been identified and has been termed Pattern-1 for first pattern gene or PATN1 for short. A dominant mutation (PATN1) was identified that is associated with increased amount of white in horses that also have the LP allele.

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Grey and Lp

One of the main 'enemies' to spotted breeding is the Grey Gene (G).  If this is inherited, then any pattern present at birth (and this is quite often very loud) will disappear over time.  This earns the name 'fader' as the colour will fade away.  It may happen over a period of months, or years, but eventually the G carrying horse will appear white.  This usually happens from front to back, finishing on the legs, with spots roaning before disappearing completely. Only when the horse is clipped, or washed, will the spots on the flesh beneath become apparent.

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01

Spotted Genetics—an Introduction

This is the first in an informative series of articles written for those new to genetics and the spotted coat colour pattern possibilities.

What will I get?

This is one of the most frequently asked questions, "what will I get coat colour-wise, if I put my mare to a spotted stallion?  There are many different factors that contribute to the inheritance of a spotted coat pattern.

There is no guarantee of coat pattern when crossing two spotted horses; it can result in solid coloured as well as spotted foals; just as a spotted and a solid horse very often produce a spotted foal when bred to one another. 

If a foal appears to have been born solid, the characteristics above may start to appear (or be present) and may indicate that the horse/pony will 'colour out', and gain more spotted patterning, as it gets older.

 

Genetics Basic Terminology

Chromosomes come in pairs, and horses have 31 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes (X and Y). One copy of each chromosome comes from the sire, and one copy comes from the dam.

A gene is a short length of DNA found on a chromosome that codes for a particular characteristic or protein.

Alleles are variations of the same gene.  A simple example would be eye colour in humans—eye colour is the gene but blue, green, brown etc. are alleles.

Alleles can be dominant or recessive.
 
Dominant alleles will be expressed even if a recessive allele is present.
Recessive alleles will be overridden by the presence of a dominant allele.


Two recessive alleles (no dominant) need to be present for the recessive characteristic to be expressed in the phenotype.


The phenotype is the outward expression of a gene (i.e. the physical appearance).


The genotype is a set of paired symbols used to represent the alleles present. The genotype can be homozygous (the same, BB or bb) or heterozygous (different, Bb).
 
The two genes that have so far been discovered to be responsible for producing spotted coat patterns are LP and PATN1.  There are many modifiers— research into which is currently ongoing.

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02

Spotted Genetics—LP 

Most breeders of spotted equines are aiming for a particular coat pattern and/or colour.  This is usually driven by marketplace demands, but is also down to personal taste for some breeders.


The added ‘spice’ to this is that there is no guarantee of coat pattern when crossing two spotted horses; it can result in anything from a solid to a completely white-born few spot.  Every breeding resets the ‘chance’ dice, so using ‘% possibilities’ doesn’t always go in the breeder’s favour!

 

I for one, have been on the receiving end of these chance possibilities—one leopard mare I owned produced two solid foals when put to a leopard stallion and a solid stallion.  Neither foal was spotted.  I decided to load the dice in my favour and use a fewspot stallion (twice)—the result both times was a fewspot!!!  I never did get my spotted foal from that mare!


The two genes that have so far been discovered to be responsible for producing spotted coat patterns are LP and PATN1.  


If the mare and stallion have been tested for LP and PATN1, then you have further knowledge on which to base future breeding choices.


The LP mutation (a mutation is a particular representation of a gene) was discovered in 2013 by Bellone et al..  This was a huge step in spotted equine breeding, as it meant that there was a scientific test to ascertain whether or not a particular animal carried the spotting gene.  This mutation is also linked with congenital stationary night blindness (CSNB) which we cover in an article further down the page.


The Bellone et al (2013) research paper is available online at:  
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0078280#s1


The LP mutation must be present in order for the equine to express characteristics and/or a spotted coat pattern. Heterozygous ponies that carry one copy of LP— LPlp will exhibit some form of spotting pattern and/or characteristics.  This can be anything on a wide range from those that are full leopard right down to those with minimal characteristics.  There are many other factors that affect the expression of LP.


All these foals below are heterozygous for LP— so carry one copy of the gene—LPlp:
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

03

Spotted Genetics—PATN1

The previous articles have dealt with the basics of inheritance, and the LP gene.   In this article the PATN1 gene and modifiers will be discussed.


PATN1 was the second gene which was discovered to contribute to the spotted coat colour pattern in equines.  Appaloosa Pattern-1 is a modifier of the leopard complex spotting (LP) and controls the amount of white in the coat pattern.

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