STR Analysis of Chimera in a False Negative Paternity Test
With the development of technology,more and more cases of chimerism have been found in paternity tests.At present,blood sample is the most commonly used for paternity testing,and a few institutions take oral swabs as samples.After ruling out the possibility of iatrogenic artificial chimerism and sample contamination,the presence of multiple alleles in different loci usually indicates congenital chimerism.However,if the chimera blood contains only one type of cell population,the autosomal STR typing of the blood sample will not be abnormal,and it is easy to draw a false identification conclusion that excludes relatives.This paper reports a very rare case of chimera.In this case,gene chimerism was detected only in seminal stain,and no chimerism was found in blood samples,hair and saliva spots.When blood was used for paternity test,the tested father was excluded as the biological father of the two children.However,when sperm plaques were used as samples,it was supported that the tested father was the biological father of the two children.The analysis suggests that the father is a chimera formed by the parthenogenetic division of the mother's germ cells.Cases of chimerism,which occurs after the fusion of two fertilized eggs,have been reported only in germ cells and not in blood cells.For forensic identification,it is necessary to improve the understanding of chimerism.When the phenomenon of chimerism is suspected,the samples from different parts should be extracted and compared as far as possible.
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