| As the molecular chaperone, HSP70 takes significant role in the physiological function of the body under the normal and stressed conditions and it can participate in the repair of damaged cells, depolymerization of the abnormal agrin, resistance to the apoptosis resulted by the stress and resistance to different kinds of adverse environmental factors for the organism. Taking HSP70-1 as the candidate gene, this experiment searched SNPs throughout the code region of the whole genes and analyzed the relation between these SNPs and Holstein heat resistance and mastitis resistance.I. Genetic Polymorphism of HSP70-1 Gene and Population Genetic Characteristics in HolsteinAccording to the gene sequence of HSP70-1 with the registered number of AY149618 (19526bp)in NCBI, designed nine pairs of primers and adopted the method of integrating PCR-SSCP PCR-RFLP and CRS-RFLP to search for the polymorphic loci within the code region of HSP70-1 gene in Chinese Holstein. The G-A-C mutation at 1623bp and G-A mutation at 2409bp were found and both of them were silence mutations that caused no alteration in amino acid sequence. Chi-square test showed both loci weren't at Hardy-Weinberg disequilibrium in Chinese Holstein, which showed that both loci could be influenced by the nature or artificial selection. The polymorphic information contents at 2409bp was 0.276, belong middle polymorphism; it was 0.554 at 1623bp, as the high polymorphism. Both loci contained abundant polymorphic information contents and held the potential to be used as the molecular marker.II. Genetic Polymorphism of HSP70-1 Gene and its Correlation with Resistance to Heat in HolsteinThe experiment took the rectal temperature and erythrocyte potassium ion concentration as the heat resistance indices of Chinese Holstein. The least squares estimator in general linear model of SAS analyzed the correlation of HSP70-1 gene with resistance to heat of 127 dairy cows in three modern farms in Shandong. The association of 2409 locus and heat resistance was not significant, as well as the erythrocyte potassium ion concentration at 1623 locus. However, the gene at 1623 locus affected body temperature of Chinese Holstein during heat stress period significantly (P<0.05). The rectal temperature during the heat stress period of genotype GA was significantly lower than genotype CC and GG, so genotype GA was heat resistant. 1623 gene locus could be treated as the molecular marker to select heat assistance Chinese Holstein dairy cows.III. Genetic Polymorphism of HSP70-1 Gene and its Correlation with Resistance to Mastitis in HolsteinIt randomly adopted 253 copies of blood samples in Tianjin Experimental Dairy Farm. These samples included complete DHI data. Where, SCC(Somaic Cell Count) was proved to hold high correlation with mastitis. SCS that transferred from SCC belonged to normal distribution and it would more advantageous than SCC in the statistics. The experiment took SAS8.2 to analyze the correlation between HSP70-1 gene and SCS and with the aid of least squares estimator in general linear model built in this study, it analyzed the influence of HSP70-1 gene, environment, fetal time and seasons on SCS; the results showed that the influence of field and fetal times on SCS was quite significant (P<0.01), the influence of birth seasons and 1623bp on SCS was significant (P<0.05), and the influence of 2409bp on SCS was not significant (P>0.05); The difference genotype on 1623bp with SCS was significant and genotype CC was significantly lower than genotype GA and GG and the difference among other genotypes were not significant. Genotype CC could be determined as the mastitis resistant. 1623 locus could be treated as the molecular market of the breeding for mastitis resistance.When taking the oriented artificial selection for the certain quantity trait, it would certainly cause the breakage of gene equilibrium between the main gene of this quantity trait and the linked other genes or gene marker. This research showed that HSP70-1 gene of Holstein dairy cows were at the significant disequilibrium status (P < 0. 01); while 1623 locus genotype had the significant correction with SCS and heat resistance of Holstein dairy cows, which showed that the dairy cows were affected by the selection on the aspects of mastitis resistance and heat resistance... |
