关键词: 嵌合体, STR分型, 法庭调查

Abstract:

A congenital chimera is an organism possessing two genetically distinct cell lines either in the whole body or limited to the haemopoietic tissues. This paper described two paternity cases in which blood samples from two externally normal alleged fathers showed abnormal STR profiles that more than two alleles were assigned at one locus. To clarify the chimeric form or origin and evaluate its consequence for forensic purpose, other tissue samples of the two alleged fathers, including hair follicles, buccal mucosa, semen and urine, as well as their family member's blood samples were additionally asked to be submitted. The autosomal STR profiles from all samples of both males revealed the presence of two maternal and paternal alleles at some loci, indicating they were “whole body chimera" derived from the fertilization of two maternal nuclei and paternal sperms. The chimeric male in case 1 might be form from the merging of male-female dizygotic twins due to paternal X alleles showing on his X-STR profile. whereas the other chimeric male in case 2 might be from the merging of male-male twins due to double maternal X alleles existing on his STR profile. Y -STR profiles of the both chimeric males showed normal and consistent with their male family members. Different allelic imbalances (<50-70%) were observed in different kinds of tissue samples.

Key words: chimerism , STR profile, forensic investigation