Question

Which of the following tests is not used for detection of specific aneuploidy?

• A. FISH
• B. RT-PCR
• C. QF-PCR
• D. Microarray

Hint:

One option measures mRNA expression, not chromosome copy number.

Answer 1

The Correct Option is B

Step 1: Define aneuploidy. It is an abnormal chromosome number, such as trisomy 21, trisomy 18 or monosomy X. A test for specific aneuploidy must count or compare the dosage of whole chromosomes.
Step 2: Check each option. FISH uses chromosome-specific fluorescent probes; counting the signal dots per cell directly reveals trisomy or monosomy, so it detects aneuploidy. QF-PCR (quantitative fluorescent PCR) amplifies polymorphic short tandem repeat markers on target chromosomes and uses peak ratios to detect extra or missing copies, a standard rapid aneuploidy test. Microarray (chromosomal microarray) measures copy number across the genome and readily detects whole-chromosome gains and losses.
Step 3: Evaluate RT-PCR. Reverse transcription PCR converts mRNA into cDNA and amplifies it to measure gene expression levels. It works on transcripts, not on genomic chromosome dosage, so it is not a tool for counting chromosomes or detecting aneuploidy.
Step 4: The printed key marked microarray, but microarray (chromosomal microarray analysis) does detect aneuploidy through copy-number analysis. The technique that does not detect specific aneuploidy is RT-PCR, because it measures expression rather than chromosome number. The medically correct answer is RT-PCR (option B), and the recalled key has been corrected on this basis.