Diagnostic and therapeutic applications for Noonan Syndrome are described. The diagnostic and therapeutic applications are based on certain mutations in a RAS-specific guanine nucleotide exchange factor gene SOS1 or its expression product. The diagnostic and therapeutic applications are also based on certain mutations in a serine/threonine protein kinase gene RAFl or its expression product thereof. Also described are nucleotide sequences, amino acid sequences, probes, and primers related to RAF1 or SOS1, and variants thereof, as well as host cells expressing such variants.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with government support under Grant Nos. HL71207, HD001294, and HL074728, HL066681 awarded by the National Institutes of Health, and Contract Nos. DE-AC02-05CH11231, DE-AC52-07NA27344, and DE-AC02-06NA25396 awarded by the Department of Energy. The government has certain rights in the invention.