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Gene: HMGA2

General Information:

  • Height in animals depends on multiple factors including genes and the environment.
  • Variants in 4 genes have been shown to account for 83% of height in horses.
  • One genetic variant (a single basepair change in the HMGA2 gene) has a strong influence on height in Shetland ponies and miniature horses.
  • This test enables breeders to predict a pony’s approximate adult height before it is fully grown and to plan breedings to select for taller or shorter ponies.

Possible Genotypes:

Genotypes G/G G/A A/A
Effects: “Normal”: Ponies will reach an average height of 104 cm.

Depending on mating, offpring will be either “normal (G/G)” or “medium small (G/A)”.

“Medium small”: Ponies will reach an average height of 98 cm.

Depending on mating, all three genotypes and heights are possible (G/G, G/A, A/A) in the offspring.

“Small”: Ponies will reach an average height of 84 cm.

Depending on mating, offspring will be either “medium small (G/A)” or “small (A/A)”.


  • This variant has a strong influence on ponies and miniature horses. Other horses will not stay at the predicted heights, even with the respective genotypes. Most horse breeds have the G/G (“normal”) genotype.
  • In larger horses, other genetic variants (not all of which have been identified) have a greater impact on height. In Warmbloods, for example, a variant in the LCOLR regulatory region influences height. See the Height test – Horse for further information.

Test information: This test detects the change of a single basepair in exon 1 of the HMGA2 gene.

Frischknecht, M., Jagannathan, V., Plattet, P., Neuditschko, M., Signer-Hasler, H., Bachmann, I., Pacholewska, A., Drögemüller, C., Dietschi, E., Flury, C., Rieder, S., Leeb, T.: A Non-Synonymous HMGA2 Variant Decreases Height in Shetland Ponies and Other Small Horses. PLoS One 10:e0140749, 2015. Pubmed reference: 26474182. DOI: 10.1371/journal.pone.0140749.

Makvandi-Nejad, S., Hoffman, G.E., Allen, J.J., Chu, E., Gu, E., Chandler, A.M., Loredo, A.I., Bellone, R.R., Mezey, J.G., Brooks, S.A., Sutter, N.B.: Four loci explain 83% of size variation in the horse. PLoS One 7:e39929, 2012. Pubmed reference: 22808074. DOI: 10.1371/journal.pone.0039929.

Signer-Hasler, H., Flury, C., Haase, B., Burger, D., Simianer, H., Leeb, T., Rieder, S.: A genome-wide association study reveals loci influencing height and other conformation traits in horses. PLoS One 7:e37282, 2012. Pubmed reference: 22615965. DOI: 10.1371/journal.pone.0037282.

Further information is available at Online Mendelian Inheritance in Animals.


Gentest #: H220

Temporarily Unavailable

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