Screening of three-way crossbred combination and genetic effect analysis of the SNP in the CLPG gene in meat sheep.

In order to promote the rapid development of the meat sheep industry, a three-way crossbred combination experiment was carried out with Australian White, Dorper, and Charollais sheep as terminal male parents and the elite F1 hybrids of Australian White  × â€¯Small-tailed Han (Han), Dorper  × â€¯Han, and Charollais  × â€¯Han as female parents, which was based on the screening of a two-way crossbred combination in meat sheep. The growth performance of six groups of three-way crossbred combinations and Han lambs was measured and analyzed, and the effect of a polymorphism in the CLPG gene on the growth performance of three-way crossbred lambs was also studied. The results showed that under the same rearing conditions, weight at 3 and 6 months of age and average daily gain from birth to 3 months and from 3 to 6 months of age were all the largest for Australian  × â€¯(Charollais  × â€¯Han) crossbred lambs. They were significantly or extremely significant different from the other three-way crossbred combinations and Han lambs ( P < 0.05 , P < 0.01 ). The body height, body length, chest girth, and cannon bone circumference at 3 months of age and body length, chest girth, and cannon bone circumference at 6 months of age were also the largest for Australian  × â€¯(Charollais  × â€¯Han) crossbred lambs. Among them, body length, chest girth, and cannon bone circumference at 3 months of age were significantly different from the other three-way crossbred combinations and Han lambs ( P < 0.05 ), and body length, chest girth, and cannon bone circumference at 6 months of age were significantly or extremely significant different from the other three-way crossbred combinations and Han lambs ( P < 0.05 , P < 0.01 ). The potential genetic effects of the CLPG gene on the growth performance indicators of three-way crossbred lambs showed that a mutation site ( g .232 C   >   T ) of this gene had two genotypes: CC and CT. Among them, the data of body weights and body sizes from CT genotype individuals at birth, 3 months old, and 6 months old were significantly higher than those of CC genotype individuals, and some indicators showed significant or extremely significant differences ( P < 0.05 , P < 0.01 ), suggesting that higher growth performance was observed in individuals with T alleles. To sum up, the crossbred combination of Australian  × â€¯(Charollais  × â€¯Han) could be suggested as the optimal choice. The T allele of the CLPG gene showed potential advantages in the performance of meat production in meat sheep. Based on the current results, we recommend that the offspring of Australian  × â€¯(Charollais  × â€¯Han) with the T allele should be preferentially utilized for meat sheep production.

Study on tandem repeat sequence variation in sheep mtDNA D-loop region.

The 75-nt-long tandem repeat sequence in the control region of mtDNA of 77 individuals, of which 69 were from different indigenous sheep breeds in China and 8 were from imported breeds, was sequenced and analyzed to investigate the origin and differentiation of Chinese indigenous sheep breeds and also the genetic diversities and relationships among them. A total of 28 variable sites were detected within 309 repeated sequences, among which 7 sites were singleton variable sites with two variants, 1 site was a singleton variable site with three variants, and 20 sites were parsimony informative sites with two variants. A total of 63 haplotypes were sorted from 28 polymorphic sites, among which two main and basic haplotypes, namely, Hap 1 and Hap 3 were present at a much higher proportion, at 12.94% and 30.42%, respectively. It could be inferred that Chinese indigenous sheep breeds originated from two maternal ancestors because of the maternal inheritance characteristics of the mtDNA. Altay sheep and Kazakstan sheep are closely related and do not differentiate significantly. Mongolian sheep and Ujumuqin sheep also share a close relationship. Tibetan sheep, Mongolian sheep, and Ujumuqin sheep have lower genetic diversity than Altay sheep and Kazakstan sheep.

SNP identification and analysis in part of intron 2 of goat MSTN gene and variation within and among species.

Part of intron 2 of the myostatin (MSTN) gene of 140 goats from 24 populations and 38 sheep from 8 breeds were sequenced, and similar sequences of different species from Gene bank were also obtained to study MSTN diversity within and among species. The results indicated that there were seven polymorphic sites in the sequenced region of goat, which have not been separated by recombination (or recurrent mutation), presented complete linkage disequilibrium, and could be sorted into three haplotypes. There was no polymorphic site in the sequenced region of sheep. The haplotype diversity, nucleotide diversity, and average number of single nucleotide polymorphism (SNP) differences of goats from the South group are higher than those of North group, and the corresponding value of the Foreign group is also higher than that of Chinese. The genetic differentiation (0.7558) between the Foreign and Chinese group is significant. There are two main haplotypes of the MSTN intron 2 in the goat, which may represent two ancestral types, in support of the theory that domestic goats in the world mainly originated from two ancestors based on morphology, history, archaeology, and molecular markers. The sequence differences of the MSTN intron 2 among species are greater than those within species.

[Study on mtDNA D-loop of Chinese main indigenous sheep breeds using PCR-RFLP].

The polymorphism of mtDNA D-loop of 83 individuals from 9 Chinese indigenous sheep breeds and 2 imported sheep breeds were studied with 5 endonucleases, Hinf I, Msp I, Sau3A I, Xsp I and Taq I, using PCR-RFLP. The results indicated that there existed two basic haplotypes in the region of mtDNA D-loop. It could be inferred that Chinese indigenous sheep breeds originated from two maternal ancestors. The averaged polymorphic degree (Pi value=0.0421%) of mtDNA D-loop showed that the genetic diversity of mtDNA of Chinese indigenous sheep breeds was very poor.

Study on polymorphisms of microsatellites DNA of six Chinese indigenous sheep breeds.

The polymorphisms of 17 microsatellites loci of six indigenous sheep breeds, including Mongolian sheep, Ujumuqin sheep, Kazakstan sheep, Aletai sheep and Tibetan sheep, were studied using polypropylene gel electrophoresis in order to investigate their genetic diversity,origin, differentiation and relationships. The results indicated that there was a significant difference in genetic diversity between different loci (P < 0.01). There was no significant difference in PIC, Fis and observed heterozygosity (Obs. Het) among populations (P > 0.05), but a significant difference in gene diversity and expected heterozygosity (Exp. Het) (P < 0.05). Chinese indigenous sheep breeds had similar genetic diversity as those from Europe,but with higher inbreeding coefficient. It could be inferred from the cluster of individuals and populations that Chinese indigenous sheep breeds might originate from two ancestors. The cluster of populations showed that Mongolian sheep and Ujumuqin sheep had close relationship and did not differentiate obviously. Mongolian sheep and Tibetan sheep had far relationship and differentiated significantly. Aletai sheep differentiated from Kazakstan sheep but not significantly. Tan sheep,Aletai sheep and Tibetan sheep also had close relationships. The Fst of Chinese indigenous sheep breeds was close to some Spanish sheep breeds,but much smaller than that of other European sheep breeds. More loci and samples should be studied in the future in order to obtain more accurate results.

Study on SNP of melanocyte stimulating hormone receptor gene in several Chinese indigenous sheep breeds using DHPLC.

Single nucleotide polymorphism (SNP) of melanocyte stimulating hormone receptor (MSHR) gene was studied by sequencing and denaturing high performance liquid chromatography (DHPLC) in Mongolian sheep, Kazakstan sheep, Tan sheep and Tibetan sheep. The results showed that there is a mutation at position 317 (T317C) within the length of 415bp and the DHPLC is a high-throughput and simple method for screening this mutation. The heterozygote (TC) with shoulder peak could be detected quickly at the first time of DHPLC, and two homozygotes (TT or CC) could be discriminated easily through two times of DHPLC when each homozygous DNA was mixed with a known homozygous reference sample at the second time of DHPLC. All of the populations for this site are in Hardy-Weinberg equilibrium. The results also indicated that Mongolian sheep and Kazakstan sheep had close relationship, Tibetan sheep and Tan sheep had close relationship. The relationship among breeds was consistent with that of microsatellite DNA.

[Inheritance of head and neck color and black hoof of Boer goat].

The inheritance of head and neck color and black hoof of Boer goats and their offspring were analyzed by observing,breeding data and statistic test in the Crossbreeding and Improving Research Center of Boer goat in Qinhuangdao city. The results indicated that the color of head and neck and black hoof of Boer goat were all controlled respectively by two linked recessive genes on one autosome. The rate of crossing-over between the genes of head and neck color and black hoof was 7.5 genetic units.

[Studies of random amplified polymorphic DNA(RAPD) of main indigenous sheep breeds in China].

The genetic polymorphism and relationship of 7 indigenous sheep breeds of China and 3 imported sheep breeds were studied using random amplified polymorphic DNA (RAPD). The results indicated that the RAPD was an effective marker for the analysis of genetic relationship among sheep breeds. Among 43 arbitrary primers,35 were polymorphic. The percentage of polymorphic markers was 66.24%,which indicated that the RAPD had higher efficiency of polymorphism detection and sensitivity in studying the genetic variation among sheep breeds. The average index of genetic polymorphism for whole population (Hsp) was 0.9139,which showed that the genetic polymorphism was abundant between sheep populations. The genetic relationship between different indigenous sheep breeds in China was in accord with their localities,the results from archeology and cytogenetics and the genetic relationship between imported sheep breeds was in accord with their breeding history.