Multistep microsatellite mutation leading to father-child mismatch of FGA locus in a case of non-exclusion parentage.

A non-exclusion paternity case with a mismatch in the autosomal short tandem repeats (STR) locus FGA is reported. The genotypes of the suspected father, the mother and the questioned child in FGA locus were 18/25, 20/26 and 20/22, respectively. Examination of 38 autosomal STR loci revealed no mismatches, and the paternity index is up to 1.3618×10(6). The haplotype of 16 Y chromosomal STR in the child matched completely with that of the father. These results suggested that the suspected father is the biological father of the child and that a rare three- or four-step microsatellite mutation had occurred in the paternal allele of FGA.

Multistep microsatellite mutation in a case of non-exclusion parentage.

A non-exclusion paternity with multistep mutation in the locus D5S818 was reported. Examination of 39 autosomal short tandem repeats (STR) loci revealed a mismatch of the maternally or paternally transmitted allele in the locus D5S818 in the questioned child. The composition of the alleles of this locus in the mother, the questioned child and the alleged father are 11/13, 7/13 and 13, respectively. The sequence analysis of the regions flanking the locus D5S818 of the mother, the questioned child and the alleged father excluded the possibility of null allele as a cause of the allelic mismatch in the child. The combined paternity index of 39 autosomal STRs is up to 2.461×10(9). Genotyping of sixteen Y-STR loci in the questioned child matched completely with the alleged father. The results prove that the alleged father is the biological father of the questioned child with four-step or six-step microsatellite mutation in the locus D5S818.

Age-related DNA methylation changes for forensic age-prediction.

There is no available method of age-prediction for biological samples. The accumulating evidences indicate that DNA methylation patterns change with age. Aging resembles a developmentally regulated process that is tightly controlled by specific epigenetic modifications and age-associated methylation changes exist in human genome. In this study, three age-related methylation fragments were isolated and identified in blood of 40 donors. Age-related methylation changes with each fragment was validated and replicated in a general population sample of 65 donors over a wide age range (11-72 years). Methylation of these fragments is linearly correlated with age over a range of six decades (r = 0.80-0.88). Using average methylation of CpG sites of three fragments, a regression model that explained 95 % of the variance in age was built and is able to predict an individual's age with great accuracy (R (2 )= 0.93). The predicted value is highly correlated with the observed age in the sample (r = 0.96) and has great accuracy of average 4 years difference between predicted age and true age. This study implicates that DNA methylation can be an available biological marker of age-prediction. Further measurement of relevant markers in the genome could be a tool in routine screening to predict age of forensic biological samples.