Problem
Case: A 45-years old pregnant lady in her 12th gestational week came to your clinic worry about her fetus developing a chromosomal abnormality. As a genetic counsellor, you requested a prenatal screening testing. Results of the ultrasound show a normal fetus, while results of the blood analysis for the lady show a low PAPP-A level, which indicates presence of a chromosomal abnormality.
Result of the confirmatory cytogenetic analysis is showed below:
Y 13 18 13 18 21 21. 13 X
I. For further investigation, you decided to request FISH analysis. What sample would you request for a confirmatory test and why?
II. What is the probes type used in this FISH test for detecting aneuploidy?
III. What is the predicted karyotype ISCN diagnosis of the fetus based on FISH analysis?
IV. What is the name of the syndrome that is caused by this chromosomal abnormality?
V. What is the reason of the increased risk of chromosomsal abnormalities in this case?