| It is the man's hopeful objective to reduce production cost, improve economic benefit and increase output of animal products by raising twinning rate of cattle and sheep. Therefore, seeking major gene influencing littler size at genetic structure or gene expression has been paid a great attention to at home and abroad. FSH is a essential hormone to follicular growth, development, dominance, maturation and ovulation. But the biological effects of FSH are mediated by a specific receptor FSHR expressed on the surface of target cells, Which can transmit the message of FSH from exterior surface of cell to inside of cell. It has been discovered that prolific sheep have one significant characteristics: their ovaries are more responsive than that of monovular sheep. When prolificacy is selected in the herds the responsiveness of ewe and cow to FSH can be enhanced. These results illustrate that change of the expressive amount or structure and vitality of FSHR adjust the action of FSH. For this reason, the structure and organization of FSHR gene, especially the characteristics and difference of 5' flanking region of FSHR gene of smalltail Han sheep, dairy goat and Bos of different little size, studied in this research in order to explore the role of FSHR in the animal prolificacy.First, the primers to amplify the sequence of 5' flanking region of FSHR gene of smalltail Han sheep, Guanzhong dairy-goat, Chinese Simmental and yak were designed using the homologous sequence of Australian sheep. In order to guarantee success of amplifying 5' flanking region of different species or genera domestic animals , 3 pairs of primers were designed and employed, annealing temperatures were regulated and PCR conditions optimized also. The results proved when base-different rate is below 6.1%, using a few primers designed from the sequence of one species to amplify the homologous sequence of different species can ensure the success. The primer amplifying the sequence of partial 10th exon belonging to FSHR gene structural region of smalltail Han sheep, Guanzhong dairy goat, Chinese Simmental and yak was based on complete homology between sequences of cattle and Ovine published.All of amplified products recovered and purified from agarose gel by glassmilk as absorbent. Fusion DNA was constructed by T-vector ligated with amplifiedproduct. SEQNCE software was employed to align, compare and scan the homologous sequences of different species or genera. The results showed that the lengths difference exist among the 5' flanking regions of 4 species or genera. The sequence lengths of smalltail Han sheep, Guanzhong dairy-goat and Chinese Simmental, yak are 815bp, 817bp and 818bp respectively. The sequence lengths of 4 species or genera are the same at the 1st exon and sequenced part of 10th exon. Study on the 5' flanking region of 4 species FSHR gene showed that their genetic composition controlling gene transcription is significant different from that of human and murine. Their transcription promoter regions have the characteristics of TATA-promoter. On the 5' flanking region of their FSHR gene there is a TATA-box, a TATA-like box, a few CAAT-like box and a GC-box, but there is no pyrimidine-rich or Ink-like region near the transcription initiation site. There is also no E-box on the FSHR gene of cattle and yak. On the sequence of 5' flanking region the base-variability between species has characteristic differences at -l-50 loci and -251-440 loci. At -1?50 loci the sequence similarity between dairy-goat and cattle is great (96%), but the base-different rate of Han sheep is higher (10% and 14%). At -251-440 loci. The base variability between dairy-goat and Han sheep (7.4%) is one time higher than that between cattle and Han sheep, and between dairy goat and Han sheep (3.7% respectively). The polymorphism of 5' flanking region studied using restriction endonuclease pst I, Taq I and Haelll by PCR-RFLP. 2 alleles, A and B, and 3 genetypes, AA, AB and BB were identified by Taq I . Allele B exists as a result of sequence mutation at -387-3...
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