Doctoral Dissertation Improvement: Genetics of Human Facial Variation

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Human facial features are clearly under strong genetic control. Identical twins often have nearly indistinguishable facial features, and related individuals show notable familial resemblances. Persons affected with particular Mendelian conditions have consistently distinctive facial features. Human facial features also exhibit extensive normal variation throughout the world. Anthropologists have long been able to use morphometric measures to quantify this variation, finding many similarities within and differences among populations from around the world. While much is known about morphological variation in facial features among populations, the underlying genes that are responsible for these traits have yet to be identified. Abundant evidence suggests that some alleles have strong phenotypic effects on facial morphology, but very little is currently known about these genes. The aim of this project is to investigate the relationships among morphological variation of the face, genetic ancestry and candidate genes in a sample of admixed individuals. Through a process known as admixture mapping, it is possible to identify genes for traits which vary between the parental populations that contributed to the admixed population. To accomplish this, facial variation will be quantified from three-dimensional images using several morphometric methods and genetic variation will be measured via a panel of ancestry-informative markers. A list of candidate genes will be identified from the literature and tested for signatures of non-neutral evolution. Single-nucleotide polymorphisms in these candidate genes will be tested for effects on facial variation while controlling for genetic stratification resulting from admixture. The results of these analyses will be the identification of some of the first genes involved in normal variation in facial morphology. Given the evolutionary and anthropological significance of the human face, understanding normal variation in human facial features is an important direction for future genetic exploration. Finding genes involved in facial variation can and should provide new insights into our understanding of modern human variation and presents a new avenue for investigating the evolution of human facial variation.