| Human genome is a very stable system. There are 46 chromosomes, same number of genes, indistinctive gene distribution, roughly identical nucleotide sequence in different populations and individuals .The stability of genomic structure just ensure the homogenicity and stability of human being as a species,and also show that the present genomic determination is deliberate or representative. However, human genome is a variant system since variation took place continuously in DNA sequences of genome during the long evolutional process. These variations may be harmful, beneficial or neutral, of which some were retained and consequently induced variation or polymorphism of genome in different populations or individuals. Except identical twin, the genomes from any two individuals are not absolutely the same. The genetic polymorphism of human genome manifested partly in variations of copy numbers of repetitive sequence. However, the other more common polymorphism originated from alteration of single base in genome, which consist of not only deletion and/or insertion of single base but mainly include substitution of single base, i.e. single nucleotide polymorphism, (SNP). Human genome project (HGP) was formally started in 1990 and sequencing task was accomplished before the predicted time, namely 2005. Advancement of genomic sequencing made it possible to extensively, deeply study genomic variation or single nucleotide polymorphism, (SNP) in populations or individuals. People increasingly believed that this kind of polymorphism is conducive to explaining the variation of individual phenotypes, susceptibility of diseases and complex diseases in particular of different populations and individuals, resistance to variable drugs and reaction to environmental factors. Therefore, finding and investigating SNP has become one of the constitutions and objectives of human genome project. [35-36]。There are more than 3 million SNPs in human genome, of which twenty thousand exist in encoding regions. LandorE from MIT in USA put forward and designated SNP as the third generation genetic marker. SNPs consist of more information associated with the susceptibility of diseases. With the extensive use of SNPs, it will become a new method to study the variability of genome and discriminate and determine disease-associated genes. Pregnancy-induced hypertension is a characteristic disease during pregnancy period. Meanwhile, it is one of diseases that seriously threatened maternal and perinatal safety and is still one of the main causes of maternal and perinatal mortality so far. There were many pathogenetic hypotheses about pregnancy-induced hypertension, but it is not clear yet. Therefore, the research aimed at its pathogenesis and the appropriate prevention and cure is extremely important. Tension of sympthetic nerve in the PIH patients is intensified and the concentration of catecholamine in blood was increased, especially NE. NE-induced vasoconstriction and vasodilatation are manifested through the relevant receptors, of which β2-AR can induce lossening of uteri smooth muscles, dilate uterine artery and moderate the uterine constriction caused by catecholamine. [37-38] Some study [39]have been reported that the binding numbers of β2-AR increased slightly in peripheral lymphocytes of PIH patients compared with normal pregnant women. Although the variation was not statistically significant, you still cannot rule out this possibility that the variable binding numbers of β2-AR may result in the occurrence of PIH. PIH has strong genetic tendency. Gene variation may be one of the main pathogenic factors of PIH. We have found several polymorphism markers in gene constitution of human β2-AR gene. The amino acid located at Arg16Gly,Gla27Glu drew much attention now. The genetic variation, which leads to an exchange of arginine to glycine at position 16, may be result in the change of function of β2-AR gene and then influence the blood pressure, which has been reported at this point. The function of β2-AR variation in the PIH and... |
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