A cytosine/thymosine (C/T) polymorphism was discovered 13 nucleotides upstream from the 5′ end of the tandem array of the D5S818 locus (−13 SNP). The −13 SNP coincidently creates a restriction site polymorphism for the restriction endonuclease SnaB1 that is tightly linked to the D5S818 tandem array. RFLP mapping of the −13 SNP was used to characterize 40 D5S818 addition/deletion mutations encountered in routine parentage testing. Most mutations showed paternal bias and single repeat changes to the tandem array. In 19 instances, it was possible to identify the parental allele that underwent the mutation. Alleles 13 and 14 were especially prone to mutation whereas allele #11 was unexpectedly resistant.
- D5S818 STR locus
- Parentage testing