Physiological and genetic mechanisms underlying variation in growth within species

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Within all species, many traits show continuous variation between individuals (e.g., body mass) rather than discrete one-or-the-other states (e.g., blood type).  Continuous traits are determined by both the environment and a potentially large number of genes.  The goal of my research programme is to understand the physiological and genetic factors underlying within-species variation in growth.  I will achieve this by studying specific physiological pathways and relating physiological variation to variation in body size (e.g., mass, bone length, etc) in mice.  The focus of my programme will be on naturally-occurring variation among healthy individuals, and not on the effects of artificial genetic modifications.      A great deal of work in this field has examined inbred mice.  Although inbred animals offer advantages from a genetic perspective, it is not clear how representative they are of the 'real world'.  I will therefore study both inbred and outbred populations of mice in the laboratory, and then use this work to generate hypotheses which I will test in natural populations of rodents.  This will put the genetic and physiological results in an ecological context (e.g., what are the consequences of genetic and physiological variation for an animal's ability to survive and reproduce?).      My research will yield insight into the pathways through which genetic variation is related to variation in whole-animal traits such as body size.  Such information is crucial to understanding why some people are more susceptible to a particular disease than others.  For example, one of the physiological pathways I intend to study influences bone mineral density, and so variation in this pathway may affect susceptibility to osteoporosis.  Understanding the mechanisms responsible for within-species variation is also important to predicting how natural populations will respond to a changing environment, since genetic variation is the raw material by which adaptation may be achieved.