| PCR-SSCP was used to research the genetic variation of the DGAT2 gene and Leptin gene in two hundreds Chinese Holstein. The relationship between genetic markers and the milk production traits were analyzed. The aim was to find perfect markers which can provide theoretical base for breeding of Chinese Holstein. The results were as follows:1. The analyze on polymorphism and sequence on the exon 4 region of DGAT2 gene Two genotypes AA and AB were found in PCR amplification region of the premier DGAT2P2 in Chinese Holstein, and the genotype frequencies were 0.8450, 0.1550 in Chinese Holstein. Sequence for the region demonstrated that there was one mutation with 481bp(G→A) in the AA genotype.2. The analyzs on polymorphism and sequence on the Intron 5 region of DGAT2 gene Four genotypes AA, BB, AB and AC were found in PCR amplification region of the premier DGAT2P4 in Chinese Holstein, and the genotype frequencies were 0.0600, 0.5200, 0.3250 and 0.0950. At the positions 132 bp (C→T) and 177bp (A→G) were two mutations in the AA genotype. There was one mutation with the position 185 bp (A→T) in the AC genotype.3. The analyzs on polymorphism and sequence on the Intron 6 region of DGAT2 gene Three genotypes KK, MM and KM were found in PCR amplification region of the premier DGAT2P5 in Chinese Holstein, and the genotype frequencies were 0.5600,0.2150,0.2250. There were five mutations with the position 1740 bp (C→T), 1766 bp (added A), 1927 bp (G→A), 2012 bp (T→G), 2065 bp (T→G) in the MM genotype.4. The analyzs on polymorphism and sequence on 5'flank region of Leptin gene Three genotypes AA, BB and AB were found in PCR amplification region of the premier LeptinP1 in Chinese Holstein, and the genotype frequencies were 0.5000, 0.1950 and 0.3050. There was one mutation with the position 1547 bp (C→G) in the BB genotype.5. The analyzs on polymorphism and sequence on exon 2 region of Leptin gene Three genotypes AA, BB and AB were found in PCR amplification region of the premier LeptinP2 in Chinese Holstein, and the genotype frequencies were 0.5350, 0.1400 and 0.3250. Sequence for the region demonstrated that there was one mutation, which was (C→T) in position 204 bp in the BB genotype.6. The analyzs on polymorphism and sequence on intron 2 region of Leptin gene Three genotypes AA, BB and AB were found in PCR amplification region of the premier LeptinP3 in Chinese Holstein, and the genotype frequencies were 0.6250, 0.0800 and 0.2950. At the positions 106 bp (C→A)and 109 bp (T→A) were two mutations in the AA genotype.7. The analyzs on polymorphism and sequence on exon 3 region of Leptin gene Two genotypes AA and AB were found in PCR amplification region of the premier LeptinP4 in Chinese Holstein, and the genotype frequencies were 0.8100, 0.1900. At the positions 96 bp (C→T) was one mutation in the AA genotype. There were three mutations with the position 268 bp (T→C), 253bp(C→T) and 352bp(C→T)in the AB genotype.8. The relationship between the polymorphism and milk production traits We chose the DGAT2 gene and Leptin gene as candidate genes to study milk production traits in Chinese Holstein. The study showed that in DGAT2P2 amplified fragment, individuals with genotype AB had a significant higher average milk yield than that of genotype AA(P<0.01), No significant effect of different genotypes on their milk protein and milk fat was found(P>0.05). In DGAT2P4 amplified fragment, individuals with genotype AC had a significant higher average milk yield and milk fat percentage than that of genotypeBB and genotype AB(P<0.01 or P<0.05), and no significant effect of different genotypes on their protein content(P>0.05). In DGAT2P5 amplified fragment, individuals with genotype MM had a significant higher average milk yield than that of genotypeKK and genotype KM (P<0.01), and no significant effect of different genotypes on their protein content and fat content(P>0.05). In LeptinP1 amplified fragment, individuals with genotype BB had a significant higher average milk yield and milk fat percentage than that of genotype AA and genotype AB(P<0.01 or P<0.05), and there was no significant effect of different genotypes on their protein conten(tP>0.05). In LeptinP2 amplified fragment, individuals with genotype BB had a significant higher average milk yield , milk fat percentage and milk protein content than that of genotype AA (P<0.01 or P<0.05). In LeptinP3 amplified fragment, individuals with genotype BB had a significant higher average milk yield and milk protein content than that of genotype AA (P<0.01 or P<0.05), there was no significant effect of different genotypes on their fat conten(tP>0.05). In LeptinP4 amplified fragment, individuals with genotype AB had a significant higher average milk yield , milk fat percentage and milk protein content than that of genotype AA (P<0.01 or P<0.05). So DGAT2 gene and Leptin gene were suit to be MAS of Chinese Holstein.
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