Such gross somatic mosaicism was not observed in three other lines examined, further emphasizing a role for flanking DNA in modulating repeat stability.
Furthermore, the only abnormal genes were found in abnormal lung and kidney tissue, arguing against genetic mosaicism.
Specifically, in 2% of patients, the mutated TSC gene is not detected in either parent because of germline mosaicism.
We do occasionally find mosaicism in chorion villous cells obtained by the CVS test at 12 weeks gestation.
Another feature of fragile X syndrome is that mosaicism is present in 15 to 20 percent of those affected by the condition.