• About This Guide
  
• How This Guide is Being Developed
  
• Philosophy of this guide
  
• Using this Guide
  
• Thinking Scientifically
  
• About the Author
  
• Documented Genes
  
• What is a documented gene?
  
• Black/Red (MC1R)
  
• Bay (ASIP)
  
• Cream/Pearl (SLC45A2)
  
• Dun (TBX3)
  
• Gray (STX17)
  
• Silver (PMEL17)
  
• Champagne (SLC36A1)
  
• Roan/Tobiano/Sabino/White Spotting (KIT)
  
• Splash White (MITF/PAX3)
  
• Leopard Complex (TRPM1/ECA3P)
  
• Frame (EDNRB)
  
• Tiger Eye (SLC24A5)
  
• Height Regulation (HMGA2/LCORL)
  
• Mushroom (MFSD12)
  
• Hypothetical Genes
  
• What is a hypothetical gene?
  
• Borrowed Genes
  
• Glossaries
  
• Glossary of Colors
  
• Glossary of Terms
  

Using this Guide

• Last updated: 2026-01-14

  This guide is divided into Documented Genes, Hypothetical Genes, Fantasy Genes, Genetic Disorders and Nonstandard Expression. Documented genes have been identified by geneticists and their location published in academic papers. Often testing is available for these genes. 

  
  

  Hypothetical genes range from well supported genes that almost certainly exist in horses but have not been documented yet, to unsupported genes which almost certainly do not exist in horses but could theoretically be possible using genetic engineering. Fantasy genes are scientifically impossible genes found in HorseGeneticsGame.com and are not intended to reflect any real life genes.

  
  

  Genetic Disorders are found in real life horses and are important for all horses lovers to be educated on but are not found in HorseGeneticsGame.com. Nonstandard expression includes somatic mutations, brindle and other oddities.

  
  

  If you are a HGG member all of the categories except Genetic Disorders are useful for you to be acquainted with. If you are looking to learn about real horses the Documented and Genetic Disorders categories are the most important to learn about, with the Well Supported Hypothetical Genes also being very useful to learn.