Dr. Tom MacCarthy
In his work, Tom investigated the evolution of sex determination gene networks using a modelling approach. He noted that sex determination mechanisms offered a good model for studying gene network evolution because, among other reasons, they evolve rapidly.
He focused on the potential for evolutionary change of the existing Drosophila sex determination gene network. With the aid of a synchronous logical model, he deifined theoretical concepts such as a network-specific form of mutation, as well as a notion of functional equivalence between networks. Applying this theoretical framework to the sex determination mechanism, Tom found that sex determination networks generally exist within large sets of functionally equivalent networks all of which satisfy the sex determination task. These large sets are in turn composed of subsets which are mutationally related, suggesting a high degree of flexibility is available without compromising the core functionality. His technique for finding functional equivalence between networks suggested a general method for gene network reconstruction.
Lastly, Tom presented a hierarchical model that integrates population genetics techniques with network dynamics. This model consists of a core population genetics simulation within which parameters such as genotype sex fitness are calculated from the corresponding network dynamics. The model was used to investigate the early evolution of sex determination networks. Following from a hypothesis proposed by Wilkins (1995), he made the assumption that sex determination networks have evolved in a retrograde manner from bottom to top. Starting from a simplest possible ancestral system, based on a single locus, he explored the way in which more complex systems, involving two or three loci, could have evolved.
Currently, Tom has been awarded the position of Assistant Professor at the Department of Applied Mathematics and Statistics at Stony Brook University in New York, USA.
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