An unusual occurrence of repeated single allele variation on Y-STR locus DYS458

Six brothers were accused of gagging and raping a woman. A single male Y-STR profile was obtained from vaginal smear swab and clothes of the victim, which did not match with the DNA profile of the accused brothers. As a reference point, the blood sample of their father (aged 87years) was also analyzed with the same kit. The Y-STR haplotype of all six brothers was found to be the same as that of their father except at locus DYS458. At this locus, while the eldest, second and fourth siblings share allele 18 with their father, a loss of one repeat (allele 17 instead of 18) is observed in the third son while fifth and sixth siblings have allele 19 representing a gain of one repeat. Thus, two changes viz. a gain (twice) and loss of one repeat at this locus in one generation is both interesting and unusual.