“…Garza-Brenner et al (5) selected a group of 19 genes that participate in the dopamine and serotonin pathway, and through a protein-protein interaction (PPI) analysis, they identified four new interacting candidate genes (POMC, NPY, SLC18A2, and FOSFBJ), of which POMC, SLC18A2 and DRD3, HTR2A (selected based on their function) revealed SNPs associated with Exit Velocity (EV) and Pen Score (PS), which are measurements of bovine temperament in a population of Charolais cattle. The same group found that the variations in these genes (DRD3, HTR2A, and POMC) had an effect on bovine growth (birth weight) in a population of Charolais cattle, showing that the identified variations not only had an effect on bovine temperament but also on live weight traits (6) . Similarly, with the objective of evaluating the potential relationship of two of these SNPs in the DRD3 and HTR2A genes with bovine temperament and growth characteristics, and feed efficiency, a population of Angus, Brangus, and Charolais cattle with temperament assessments was analysed; the results indicated that there was no association with EV and PS, but the SNP in the HTR2A gene was associated with feed efficiency in Brangus cattle (7) .…”