Related Experiment Video
Updated: Aug 16, 2026

Multi-Locus Sequencing for Strain Typing of Toxoplasma gondii
Published on: May 26, 2026
Major histocompatibility complex locus DRA polymorphism in the endangered Sorraia horse and related breeds
1Universidade de Lisboa, Faculdade de Ciências, Departamento de Biologia Animal, Lisboa, Portugal. cmluis@fc.ul.pt
Abstract:
The major histocompatibility complex (MHC) genes play well-defined roles in eliciting immune responses and combating infectious diseases. This genetic system is among the most polymorphic. The extent of genetic variation within a population has been directly correlated with fitness for many traits. The MHC class II locus DRA polymorphism was analysed in the endangered Sorraia horse, two other Portuguese and four New World horse breeds considered to be historically close to the Sorraia. Comparison of the Sorraia with other breeds demonstrated less MHC variation among Sorraia horses. If DRA polymorphism provides greater disease resistance, selective breeding to increase MHC polymorphism may increase fitness of this population.
Related Concept Videos
Multiple Allele Traits
Incomplete Dominance
Epistasis
Background and Environment Affect Phenotype
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
Frequency-dependent Selection
Pedigree Analysis

