Spotlighting two of the most prevalent and most researched genetically based disabilities - Down syndrome and Fragile X syndrome - this cutting-edge text clarifies the distinct speech and language issues associated with each disorder and helps readers conduct individualized assessment and intervention.An essential upper-level textbook and an invaluable professional reference, this book gives readers the up-to-date research and clinical insight they need to: fully understand both disabilities - the behaviors, characteristics, genetics, and treatments associated with each; see how speech and language develop across the lifespan, from infancy to adulthood; apply principles of effective assessment with people from every age group; use specific interventions to support key aspects of speech and language development; tailor assessment and intervention to an individual's communicative needs and abilities; tune into the family's perspective and encourage their ongoing involvement; and examine other disorders by using this research as a model for future practice.Authoritative contributions from more than 15 leading experts prepare readers for effective clinical practice, and the ""directions for research"" sections throughout the book help researchers shape future studies and move the field forward. A necessary resource for SLPs, pediatricians, AAC specialists, and early interventionists, this definitive volume is key to supporting the communicative competence of people with Down syndrome and Fragile X syndrome at every stage of life.