| The topic mainly concerns about children patients short tandem repeat change after virus infection. At present the virus infection has overrun the infection of other microorganism. There are 400 hundred other kinds of infection which human-being can suffer a lot.90 percent of the common respiratory tract infection is the virus infection .The virus infection has effects on human body directly or through response to immunization, resulting in various symptoms and complication after infection, threatening the children's health even their lives. The research selects respiratory syncytial virus (RSV) and Adenovirus (ADV) of the common virus infection of children as studying object, analysis of gene polymorphism of——D5S818 of DNA short tandem repetitive sequence. The aim is to discuss the change of D5S818 locus of patients with RSV or ADV infection and the relevance of immunological function as well as its interrelated clinical representation, and that the influence of body is illustrated from the perspective of gene and lay the solid foundation for further interpreting the mechanism of virus infection. Respiratory syncytial virus and adenovirus are two causes of pediatric common lower respiratory tract infection, threatening the health of children. Virus infective disease may cause inapparent infection and the infection of lasting chronicity and a series clinical situation, in addition to the probable tissue damage of acute period. DNA virus might directly intergrate with the host cell. RNA virus gene might integrate with the host cells through reverse transcriptase. Some research show that chronic inflammation may induce the duplicating templat damage of RNA and DNA due to the chronic inflammation, resulting in the errors of duplicating DNA and the occurrence of mutation of DNA. Therefore during the period of pediatric virus infection, the study of the variety short tandem repeat series particularly in repeated infective children has very important significance. Short tandem repeat series repeated with repeated unit's length 2-6bp is called microsatellite, namely simple sequences repeats which is usually called STR or MS, STR or MS was discovered by Weber in 1989 through the way of PCR amplification and direct sequencing. STR are widely distributed humankind genome mostly in non-coding region, a few coding region, whole biological functions are not completely illustrated. In recent years, the study of STR has become a hot topic both domestically and abroad. STR stands for instability region of genome, whose mutation frequency is higher than that of non-repeated DNA sequence. Microsatellite instability of STR is simple repeat sequence change due to gene mutation of mismatch repair. Often manifesting the increase and decrease of repeated unit. Discuss the Polymorphism of DNA short tandem repeat (STR) in infants with respiratory syncytial virus (RSV) infection. Method Take throat swab from the infants with virus infection in order to separate respiratory syncytial virus. DNA is extracted from peripheral venous of these infections, amplified with locus D5S818 through polymerase chain reaction (PCR), analysed with photographic system after polyacrylamide gel electrophoresis. Discuss polymorphism of fragment length of D5S818 and the relevance of clinic situation to RSV infection .Results It is found that after the RSV infection, there is obvious difference between infants with RSV infection and normal contrast group in D5S818 locus allele frequency .The repetition copy number ＜12 and ≥12of AGAT in RSV infected infants has something to do with clinic symptom and course, the mixed degree in group of RSV is obviously lower than that of contrast group. Conclusion Virus infection may change short tandem repeat. Following one or more repeated sequence change of base of STR, DNA chain continue to keep its stability. STR has higher mutation rate (10-4-10-5)and transcription, which made STR less stable . Most STR has no function of coding, maybe they have activating matter, reco...
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