Lecture 1 Introduction to Mendelian and Molecular Genetics

The two most influential biologists in history, Darwin and Mendel, were contemporaries and yet the initial acceptance of their ideas suffered very different fates. In 1859, Darwin published his Origin of Species. It was an instant classic, with the initial printing selling out within a day of its publication. His work had an immediate impact that restructured biology. However, Darwin’s theory of evolution by natural selection, as he originally presented it, was not without problems. In particular, Darwin had great difficulty dealing with the issue of inheritance. He fell back on the standard model of his day, blending inheritance. Essentially, both parents contribute fluids to the offspring, and these fluids contain the genetic material, which is blended to generate the new offspring. Mathematically, if z denotes the phenotypic value of an individual, with subscripts for father (f ), mother (m) and offspring (o), then blending inheritance implies zo = (zm + zf )/2 (1.1)