possible to develop a test which would quickly indicate the fetus' sex. This would benefit parents whose only option is to have no children or to have only girls. Confirming gender in children with ambiguous genitalia is another medical reason for using the test. A quick examination of the X and Y chromosomes of the child would indicate whether genetically the child is male or female. As yet, Willard has been unable to develop a probe for chromosome 21. Down's Syndrome results from three copies of chromosome 21 (trisomy 21). "I think we'll know within a year whether a test to detect trisomy 21 is feasible, " he says hopefully. The other six chromosome probes which Willard has developed do not immediately lend themselves to diagnostic tests, except for certain cancers, he says. "We have a probe for chromosome 7 and we know that trisomy 7 is a signal for certain typesof cancer. Chromosome abnormalities of all kinds are a signpost of tumors." Theoretically, an oncologist could use a chromosome probe test to examine tissue andobtain a reading for a specific cancer. " It wouldn't suggest a mode of therapy," he points out, "but would be a speedy test and would have prognostic implications for the kind of tumor discovered." As a basic research tool, Willard's probes could be used to develop a genetic linkage map for human chromosomes. "It's important to know the location of genes in the human genome, particularly disease genes. The leading approach to try to sort out disease genes is to use genetic linkage. Because our sequences are at the centromere it would allow us to develop a map." The third application for the probes is in forensic biology. Willard believes his markers are as unique to each each individual as are fingerprints. According to the geneticist, it will be possible to make a DNA 'fingerprint' from blood or sperm, whichcould be used as evidence in rape or murder cases. "We haven't yet done the analysis which confirms that our p...
