MUTATION CASES IN THE PATERNITY TESTS IDENTIFIED USING 15 AUTOSOMAL STR MARKERS

AIM

As well known, the mutations of the STR loci revealed in resolving the identification, disputed paternity/mothernity, kinship, etc. cases reduce to some extent the reliability of the results and deliver a certain difficulty in preparation of an accurate expert opinion. Therefore, information on the facts of detection of such allelic variations has great practical importance.

MATERIAL AND METHODS

DNA profiles of 250 family cases of the disputed paternity tests obtained by PCR amplification.

RESULTS

In this study we found mutated alleles in two cases on FGA, in two cases on D19S433, in one case on D13S317 and in one case on D5S818 locus. The mutation cases at the FGA locus can be represented as: (1) Ch1(17)=AF1(20) – 3 repeat or Ch1(17)=AF1(23) – 6 repeat (multi-step “del” mutations), (2) Ch2(25)=AF2(26) – 1 repeat (one-step “del” mutation) (hereinafter Ch – child, AF – alleged father, AM – alleged mother); at the D19S433 locus as: (1) Ch1(15.2)=AF1(16.2) – 1 repeat, (2) Ch2(15.2)=AM2(13) + 2 repeat+2 b.p. or  Ch2(15.2)=AM2(13) + 3 repeat – 2 b.p.; mutation case at the D13S317 locus can be represented as deletion leading to reduction of paternal allele size: Ch1(12)=AM(13) – 1 repeat.  The mutaton case at the D5S818 locus can be explained as follows: (1) Ch(12)=AF(11) + 1 repeat (allele size extension) and (2) Ch(12)=AF(13) – 1 repeat (allele size reduction). Moreover, in one case three-allelic profile on D21S11 locus has been observed indicating three copies of chromosome 21, which supported existing Down’s syndrome phenotype.

CONCLUSIONS

In five cases more likely these mutations affected the paternal alleles, in one case the maternal allele. For each case possible mutation formation ways scheme was proposed. It is supposed that these meiotic mutations occurred during replication according to the gene conversion or DNA crossover models (Immel et al., 2004) or strand-slippage replication mechanism (Jobling, 2004) as stepwise mutation process.