title: [Calculation of likelihood ratio for X-STR typing in kinship testing].
abstract: OBJECTIVE
  To deduce the calculation formulae of likelihood ratio for kinship testing with X-short tandem repeat (X-STR) typing.
  
  
  METHODS
  With the identity by decent coefficient of different relationships, the joint genotypic probability of two individuals with specific genotypes was calculated as X value, and then the joint genotypic probability of two unrelated individuals was calculated as Y value; therefore, the likelihood ratio value (X/Y) was obtained.
  
  
  RESULTS
  The calculation formulae of the likelihood ratio for different genotype combinations of the female-female, female-male and male-male genetic relationships were derived and verified by real cases.
  
  
  CONCLUSIONS
  The calculation formulae are simple and accurate to evaluate the likelihood ratio for two individuals' genetic relationship with X-STR typing. The formulae provide the basic potential value for the difficult kinship testing with X-STR loci.
authors.affiliation: Department of Forensic Medicine, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China. fayizym@163.com
authors.forename: Yin-Ming
authors.initials: YM
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Sun
mesh_terms: D000465:Algorithms; D000483:Alleles; D041321:Chromosomes, Human, X / Q000235:genetics*; D005260:Female; D053803:Forensic Genetics; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D016133:Polymerase Chain Reaction