DISSERTATION RESEARCH: Individual variation and male-female dimorphism: the role of testosterone and gene expression

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Males and females have nearly identical genomes, yet males and females can differ dramatically in appearance, physiology, and behavior. The proximate explanation for sex differences in phenotype is differences in gene expression, i.e., which genes are ?turned on or off? in males and females. But exactly how gender affects gene expression is an open question where much remains to be learned. Hormones such as testosterone are likely candidates for controlling differences in gene expression of genes in males and females. To date much of the research in this area has focused on experimental manipulation of hormones, rather than on the role of natural, individual variation in levels of circulating hormone. The research supported by this award asks two primary questions: (1) what genes and gene networks are affected by natural, individual variation in testosterone phenotype, and (2) how do males and females differ in affected genes and gene networks? The dark-eyed junco (Junco hyemalis), a North-American songbird, will be the subject of study because of the recent development of genomic tools in this system and the wealth of historical data on its natural history, response to testosterone, and sex differences in behavior; all studied in a wild population. Successful completion of the aims of this project will enhance our understanding of the genes and gene networks that are related to natural variation in testosterone. The research proposed here will have broader impacts because it will provide unique opportunities for undergraduate research: the preliminary stages of this research have already led to undergraduate research opportunities for four individuals from underrepresented groups.