ABSTRACT
A newborn girl with ring chromosome 1 is described. The letter reports the chromosome analysis of peripheral blood lymphocytes with 46,XX,r(1)(p36.3q44) and evidence of ring instability in umbilical cord fibroblasts.
Subject(s)
Abnormalities, Multiple/genetics , Chromosomes, Human, Pair 1 , Ring Chromosomes , Female , Humans , Infant, NewbornABSTRACT
Amniocentesis on a 32-year-old woman at risk for trisomy 21 by maternal serum triple screen showed a 46,Y,inv(X) (p22.1q24) karyotype in all cells analyzed. A blood sample was obtained from the mother for cytogenetic evaluation. Since she had the same inversion, DNA replication studies were performed to determine if the X inactivation pattern was random or not, since skewed inactivation of the inverted X might suggest that the breakpoints disrupted functional genes. DNA replication studies demonstrated that 68% of mother's cells with the inverted X were active, suggesting random X inactivation. The random X inactivation pattern suggested that the inversion is probably balanced and should not affect the fetus. A normal male was delivered at 40 weeks gestation.