The aim of this diploma thesis was to investigate the influence of milk betacasein locus (CSN2) polymorfic variants on production characteristics and milk technological qualities in Czech Simmental cattle and Holstein cattle. DNA extracted from milk of 702 cows was genotyped using PCR and RFLP methods. The genotypes A1A1, A1A2, and A2A2 had the following distribution within the population studied: A1A1 in 11,40 %, A1A2 in 8,46 %, and A2A2 in 50,14 % cows. The studied milk parameters were the milk yield (kg), protein and fat percentage and protein and fat yield (kg). The statistical evaluation was made STATISTICA 12 program. We found no statisticaly significant influence of CSN2 genotype on the selected milk yields. The results might be biased by the relatively low amount of individuals studied. Research will continue within the QJ1510339 and GAJU028/2019/ Z grant.

This thesis was developed to study the influence of polymorphic variants of the milk protein locus betacasein (BCN) on the production and technological quality of the milk. The genotypes of -casein (CSN2 gene) were determined by the PCR-RFLP analysis. The determination of genotypes AA, AB and BB was made in 731 dairy cows. The results of genotype frequencies showed that genotype BB represented roughly five times more frequently than the heterozygotes AB and thirty times more frequently than AA homozygotes in the population under study. The effect of the BCN genotypes on the production and composition of milk was analyzed in 418 samples. No statistically significant effect of genotypes or alleles was found in this section. Subsequent analysis of the influence of genotypes and allele on the coagulation and the determination of titratable ability of the milk was performed on 119 samples. The results did not confirm a statistically significant effect on milk coagulation. The yogurt test showed genotypic effects. This could mean that genotype AA is associated with higher milk acidity and AB genotype with lower. However, the results could be affected by lower frequency of the population and an uneven frequency of genotypes in the population surveyed.