Molecular karyotyping offers genetic blueprint of fetus. (Investigational Technique).

BALTIMORE -- Genetic technology has now provided a new way to do prenatal genetic screening: molecular karyotyping.

A genomic microarray that is in development allows analysis of a fetal genetic specimen at 1,400 different spots of the genome. "It's like doing 1,400 FISH [fluorescent in situ hybridization] at once," Dr. Rizwan Naeem said at the annual meeting of the American Society of Human Genetics.

The microarray molecular karyotyping technology is being developed by Spectral Genomics, said Dr. Naeem, a cytogeneticist at Baylor College of Medicine in Houston.

With an average of about 60 genetic markers per chromosome and good distribution of the markers along the entire length of each chromosome, the microarray analysis allows geneticists to assess chromosomal deletions and duplications throughout the human genome, said Dr. Naeem, who has received research support from Spectral Genomics but does not own stock in the company or receive other funding from it.

Currently, markers are spaced about 2 million to 4 million bases apart. To run a molecular karyotype, the genetic specimen and control DNA are fluorescently labeled, mixed, and then applied to a plate that holds the microarray, a series of small dots that contain a variety of DNA sequences from throughout the human ...