Mutations in organisms may arise one of two ways: as either a meiotic mutation, which appears during the production of sperm and eggs, or as a somatic mutation, which appears during the duplication of DNA that occurs during normal cell division and growth. The typical rate of somatic mutation is essentially unknown, but appears to be many times less than the rate of meiotic mutation. In short-lived organisms with limited growth, the overall mutation rate is strongly influenced by the rate of meiotic mutation. In long-lived organisms such as trees, however, cells may divide millions of times during growth. Thus, the rate of mutation may be more strongly influenced by somatic mutation.
This project will estimate the rate of somatic mutation in the large tropical tree Delonix regia. Flowers produced at the base and apex of large branches will be examined for differences in several measures of pollen fitness, and the number of cell divisions separating flowers will be estimated. These estimates will be used to determine the rate of somatic mutation per cell division and the average effect of each somatic mutation.
Knowledge of mutation rates is of fundamental importance to many areas of biology. Somatic mutation in particular can have dramatic impact on human welfare (e.g., by giving rise to cancers), and the rate of somatic mutation rate measured here may be used by other scientists seeking to determine the general likelihood of their occurrence.
