Certification of rare alleles 32.3 of D21S11 locus

Objective To certify the rare alleles (off-ladder allele, OL) found on the D21S11 locus in a case of paternity identification. Methods In order to understand the exact classification of this rare allele, the composite sequence structure, and its minimum allele frequency, molecular biology experiments, including PCR, cloned and sequencing methods, were designed to prove D21S11 locus exist rare alleles 32.3. Results The structure and frequency of rare alleles 32.3 was analysised. Sequencing analysis showed that the rare allele 32.3 of D21S11 locus of parent and child had the same nucleotide sequence structure. The composite sequence were [TCTA] 6 [TCTG] 5 [TCTA] 3 TA[TCTA] 3 TCA[TCTA] 2 TCCATA[TCTA] 11 . Conclusion The frequency of rare alleles 32.3 was lower, which will increase the likelihood ratio (paternity index, PI) in the paternity identification, and improve the non-exclusive probability in the paternity test. And also had important significance in the identification of individual.