Your GRE Question by GRE Question a Day

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Philippos Patsalis, a geneticist at the Cyprus Institute of Neurology and Genetics in Nicosia, developed a new method for the prenatal testing of Down syndrome. Down syndrome, caused by an extra copy of Chromosome 21, is the world's most common genetic condition. Earlier tests, such as amniocentesis, although effective, were invasive, a danger that resulted in miscarriage in 1 to 2% of the cases. In search of a safer alternative, researcher started testing the mother's blood. The problem with these initial tests, however, were that they involved genome sequencing, an expensive and time-consuming process.

Patsalis and his team focused their new technique around DNA methylation, which could isolate the maternal DNA from the fetal DNA. Once isolated, the researchers again used DNA methylation to more quickly identify Chromosome 21, which in turn allowed researchers to test for the presence of Trisomy 21. In addition to being quicker and less expensive, the new method was found to be 100% accurate. Patsalis thinks the method could be soon introduced in a clinical setting.

The passage suggests which of the following as drawbacks to the prenatal testing methods of Down syndrome, prior to Patsalis's new technique? Consider each of the three choices separately and select all that apply.


Invasive tests, such as amniocentesis were too expensive


Older blood testing techniques were too time-consuming


Prior tests failed to be 100% accurate

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