The biochemistry that relates genotype (DNA) and phenotype (proteins) has been most completely described for model organisms, such as the prokaryote E. coli and the eukaryotes yeast and Drosophila. While the details vary, there is great similarity in the fundamental processes among these forms of life. These similarities have permitted the application of knowledge and methods discovered using these model organisms to the study of human biochemical genetics. Our focus in this chapter is mutations that affect human phenotypes, leading to diseases.
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Genetic diseases often result from mutations that render proteins nonfunctional.
Mutations that cause disease include the full range of affected DNA from point mutations to entire chromosomes.
Most diseases result from a combination of factors that include both genetics and the environment.