This study will explore the genetics of taste and taste deficits. The sense of taste plays a crucial role in food choices, allowing people to identify beneficial foods (those with high caloric value, which are typically sweet) and foods likely to be toxic (usually bitter substances). The loss of sense of taste in older people plays a role in decreased appetite and poor nutrition. Taste deficits may adversely affect people in ways that are not well understood. This study will examine why some people (about one-fourth of all people in the United States) cannot taste a substance called phenylthiocarbamide (PTC). The inability to taste PTC is due to inherited factors that are not yet clear.
Individuals age 18 and older who can taste PTC and individuals who cannot taste PTC may be eligible for this study. Participants will taste a number of liquid solutions until they find one with a clear taste. Then they will taste another group of solutions and decide which ones have that taste and which have no taste. Finally, they will taste a third group of solutions until they find one with a different taste. About 2 tablespoons of blood will be drawn from participants for genetic tests related to the sense of taste.
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The primary goal of this study is to identify the underlying cause of deficits in the ability to taste different commonly consumed substances, including the bitter compound phenylthiocarbamide (PTC) as a model. Individuals will be tested to identify those who can and cannot taste PTC, as well as for their ability to taste a variety of sweet, sour, salty, and savory substances. Individuals will have 20 cc of blood drawn to obtain DNA. These DNA samples will then be analyzed for variation in genes whose products are known to be involved in taste perception pathways. Information about individuals' DNA sequence variation will then be correlated with their taste phenotype to identify the specific genetic variation that causes phenotypic variation, providing molecular structure-function information in taste sensory pathways.