of a genetic system to produce and maintain potentially adaptive genetic variants. There are several aspects of genetic architecture that contribute strongly to the evolvability of a system, including autonomy, mutability, coordination, epistasis, pleiotropy, polygeny, and robustness. Autonomy: the existence of quasi-independent characters with the potential for evolutionary autonomy. Mutability: the possibility that genetic mutation can occur. Coordination: a phenomenon such as development, during which many different genetic processes and changes happen at once. Epistasis: a phenomenon in which one gene is dependent on the presence of one or more "modifier" genes. Polygeny: a phenomenon in which multiple genes contribute to a particular phenotypic character. Pleiotropy: a phenomenon in which a single gene affects one or more phenotypic characteristics. Robustness: the ability of a phenotype to remain constant in spite of genetic mutation. Examples A study published in 2006 used phylogeny to compare the genetic architecture of differing human skin color. In this study, researchers were able to suggest a speculative framework for the evolutionary history underlying current-day phenotypic variation in human skin pigmentation based on the similarities and differences they found in the genotype. Evolutionary history is an important consideration in understanding the genetic basis of any trait, and this study was among the first to utilize these concepts in a paired fashion to determine information about the underlying genetics of a phenotypic trait. In 2013, a group of researchers used genome-wide association studies (GWAS) and genome-wide interaction studies (GWIS) to determine the risk of congenital heart defects in patients with Down Syndrome. Down Syndrome is a genetic disorder caused by trisomy of human chromosome 21. The current hypothesis regarding congenital heart defect phenotypes in Down Syndrome individuals is that three copies of functional genomic elements on chromosome 21 and genetic variation of chromosome 21 and non-chromosome 21 loci predispose patients to abnormal heart development. This study identified several congenital heart defect risk loci in Down Syndrome individuals, as well as three copy number variation (CNV) regions that may contribute to congenital heart defects in Down Syndrome individuals. Another study, which was published in 2014, sought to identify the genetic architecture of psychiatric disorders. The researchers in this study suggested that there are a large number of contributing loci that are related to various psychiatric disorders. Additionally, they, like many others, suggested that the genetic risk of psychiatric disorders involves the combined effects of many common variants with small