Scientists at Baylor College of Medicine in Houston are using microarrays, like the one pictured to the right, to detect chromosomal abnormalities in children. The test checks for significantly more discrepancies in the DNA, and with fewer errors, than the current common methods of karyotyping.
From MIT Tech Review:
The DNA chip used in the study performs a process known as array comparative genomic hybridization (aCGH), which involves looking for an abnormal number of copies of particular segments of DNA. Normally, humans have two copies of each segment. Having extra or missing copies can result in serious medical problems. Each DNA chip contains hundreds of single-stranded DNA segments, each embedded in a piece of glass at a precise location. The researchers then add single-stranded, fetal DNA segments, usually taken from amniotic fluid. These strands are labeled red. Single-stranded DNA reference segments, which act as a control group and are labeled green, are also added to the chip. Once the fetal and control strands are bound with the embedded DNA, the arrangement of colors on the chip is imaged and analyzed by a computer.
“Basically we measured the color signal intensity,” said Cheung. If the fetus has an extra copy of a particular segment of DNA, then the spot on the chip that corresponds to that DNA segment will appear more red than green. If the fetus is missing a DNA segment, the corresponding spot on the chip will appear more green than red. And if the fetus has the correct number of copies of the DNA segment, then the spot should appear yellow.
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