Genetic and chromosomal variation-caused inconsistencies in two parental tests

Abstract

Two special cases were reported where inconsistency between children and the fathers were observed at FGA locus. Regular additional STR tests were performed and no more inconsistency was observed in the first case. Through the following TA cloning and sequencing, the first case turned to be a two-step mutation between child and father. In the second case, however, one more inconsistency was found in the additional test at D4S2366, which was on Chr. 4 as well. Then, seven randomly selected STR-loci on Chromosome 4 were analyzed, indicating a possible maternal uniparental disomy (UPD) in the child with normal phenotype. This study emphasizes gene or chromosomal variations may mislead parentage test, especially variations like UPD that are relatively unfamiliar to investigators. If all the inconsistent loci are on the same chromosome, investigators should take UPD into consideration, and further tests, like chromosomal-specific STR-typing, should be applied to prevent pseudo-exclusions.