The invention provides tandem single nucleotide polymorphisms and methods for their use, for example, in diagnosing Down Syndrome. A request by a client application for a SIO of a server application in a different execution context is routed to the registry mechanism by the system. For example, one or more of such feature patterns may be used to define a particular speaking style, and an illustrative text-to-speech system then makes use of such a defined style to adjust the specified parameter or parameters of the synthesized speech in a non-uniform manner.