The Parameter Linkage Analysis Of The Genetic Disease Gene Location

Defferent studies have shown obviously that most human diseases relate to heredity.The objective of the study is to find the loci of human genetic diseases through linkage analysis. Various models and various statistical methods are provided in accordance with various distinguishing features of genetic diseases.The linkage analysis introduced here is used to infer the location of the disease locus on chromosomes according to some markers known their location.It suit to the pedigree data.The parameter linkage analysis need set the genetic mode,the gene frequency and the penetrance in advance,but it has advantages that others haven,t.It can calculate the recombination fraction and map distance between markers and the disease gene,whereas other methods can,t.It must certain the genetic mode of the trait in advance,but it can use defferent tactics,for example,making maximum likelihood estiminate for each possible genetic mode.Multipoint linkage analysis(using multiple markers) reduces the loss of the sample information.The closer are the markers,the more precisely is the gene localized.When the pedigrees have the missing data and multiple markers are used,the classical calculation is large.The problem is settled down because of the improvement of the algorithm. The most oftenest used linkage analysis is Lods method which is based on maximum likelihood ratio test because of the additivity of log_likelihood functon from independent observations.It is basedon model and the only unknown varible is the recombination fraction in analysis.With the development of algorithms,the increase of genetic markers and the build of the methods of haplotype analysis,the linkage analysis is useful especially for the singal locus disease.For complex disease,tactiful linkage analysis has its unreplaced function. In the eyes of theory and application,the theory of the linkage analysis(based on model)is present systematically and the data needed and the general steps are shown.It mainly includes the basic idea of linkage analysis,the modeling process,Lander-Green algorithm and data analysis etc.To map the gene responsible for Blepharophimosis Epicanthus Inversus and Ptosis sydrome (BPES) type â…  in a Chinese family.The linkage analysis is performed using the software of Mendel 5.0.The result shows that both the two_point and the multipoint linkage analysis find the disease locus.Multipoint linkage analysis can not only calculate the recombination and map distance but also localize the disease gene to one side of the marker.The more closely spaced are the markers on the chromosomal segment containing the disease locus,the accurately can one localize the disease gene.