Unfortunately, no DNA analysis had been conducted on the woman’s brother to determine what type of mutation in the DMD gene he had. The woman was investigated by molecular analysis and found to be heterozygous (A1/A2) for a microsatellite marker closely linked to the DMD gene. No relatives except the parents of the woman were available for analysis.
7. Discuss the relative advantages and disadvantages of the following diagnostic procedures, and cite types of disorders for which they are indicated or not indicated: amniocentesis, CVS, first-semester maternal serum screening, second trimester screening, noninvasive screening of cell-free fetal DNA (noninvasive prenatal screening [NIPS]).
• All pregnant women undergo a sequential screening strategy, as follows: All participate in first-trimester screening with pregnancy-associated plasma protein A (PAPP-A), human chorionic gonadotropin (hCG), and nuchal translucency. Sensitivity is 84% with a false-positive rate of 5%. Those who score positive are offered CVS, and all use it. Those who score negative are screened during the second trimester with a quadruple maternal serum screening, which has 81% sensitivity and a 5% false-positive rate. Those who score positive are offered amniocentesis, and all use it.