This article explores the genetic variability of the gene that encodes telomerase reverse transcriptase (TERT), which plays a key role in maintaining telomere length and, as a result, genome stability in various eukaryotic species. The study employs a comprehensive approach that combines phylogenetic and bioinformatic analysis with molecular-genetic research methods. The research involved the screening of genetic databases to investigate TERT gene orthologues across organisms belonging to different systematic groups. The TERT gene, which is prevalent in a wide range of eukaryotic biological species, exhibits polymorphisms that have the potential to influence TERT enzyme function and, consequently, animal phenotypes. The primary focus of this study centers on the pig TERT gene, selected as a model organism due to its genetic similarity to humans and its importance as a productive agricultural species. The article explores the exon-intron structure of the TERT gene, analyzing the size of the corresponding transcript and protein product. Furthermore, it provides data on polymorphisms in the pig TERT gene, including missense and synonymous variants. The chromosomal localization of these polymorphisms is characterized and correlated with the domain structure of the TERT enzyme. For the evaluation of the impact of polymorphisms on the structural and functional properties of the TERT enzyme, a molecular-genetic system based on the PCR-RFLP method has been developed. This PCR-RFLP system serves as a basis for subsequent experimental analyses of missense and synonymous variants in population and association studies, allowing for an assessment of the prevalence of these polymorphisms and their significance for animal phenotypes. Given the significance of further laboratory investigation of the pig TERT gene, the developed PCR-RFLP system becomes necessary for the assessment of the functional implications of the polymorphisms within this gene and the potential identification of causative ones among them. The synergy of bioinformatics and molecular-genetic methods in this study lays the groundwork for future impactful research in this field. The presented study holds promise for marker-associated selection, as it opens the way for the use of the TERT gene as a marker in the genetic improvement of agricultural animal species.