Population studies of 17 equine STR for forensic and phylogenetic analysis.

This research paper discusses an in-depth study of the genetic variations in horses with an aim to understanding their usefulness in forensic applications. The study examined 17 equine Short Tandem Repeat (STR) loci across 35 horse populations. It was found that this set of 17 STRs can effectively identify individual horses for nearly all breeds and accurately assign unknown samples to their correct origin breeds.

Exploration of Equine STR Loci

In scientific and forensic contexts, STR loci serve as valuable markers for identification due to their high variability. The horse DNA contains these short sequences of DNA that are repeated a number of times in a row. In this particular study, 17 of these were considered and their polymorphic information content was calculated across 8641 horses.

• The individual genetic variations were assessed for:
  • AHT4, AHT5, ASB2, ASB17, ASB23, CA425
  • HMS1, HMS2, HMS3, HMS6, HMS7
  • HTG4, HTG6, HTG7, HTG10
  • LEX3 and VHL20

Relevance for Forensics

Several calculations were performed to determine just how useful these loci could be for forensics.

• The power of parental exclusion: The probability that a randomly selected non-parent will be erroneously excluded as a possible parent.
• Polymorphic information content: The amount of information on genetic diversity that is provided by each STR marker.
• Expected and observed heterozygosity: Measures of genetic diversity within a population.
• Probability of identity: The chance that two randomly selected individuals in a population will have the same genetic profile for the selected STR markers.

The results showed that this set of STRs has a high discriminating power for identifying individual horses in almost all breeds.

Recognising Breeds

The study also explored how accurately the set of STRs could be used to assign unknown samples to their correct breeds of origin.

• Overall, the system was able to correctly assign individual horses to the proper breed 97.2% of the time.

Phylogenetic Analysis

On a broader level, the researchers were also interested in the genealogical relationships between different horse breeds. They found that the 17 STRs reveal significant phylogenetic signals. The detailed genetic analysis clustered the horse breeds into three groups:

• Cold-blooded draught breeds: Haflinger, Dutch draft, Friesian.
• Pony breeds: Shetland and Miniature horse, along with Falabella, Appaloosa, and Icelandic.
• Warmblood riding breeds: Together with the hot-blooded Standard-bred, Thoroughbred, and Arabian.