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The neutral and nearly neutral theories of molecular evolution 1
Published on July 31, 2022 33 min
Other Talks in the Series: Introduction to Evolutionary Biology
Hello and welcome. My name is Joseph Blelawski. I'm an evolutionary biologist. I'm cross-appointed in the Department of Biology and the Department of Mathematics and Statistics at Dalhousie University in Canada. Today, I'm going to lecture on an introduction to and a comparison of the neutral and nearly neutral theories of molecular evolution.
Before we dive into the details of those theories, we need to do a quick review of the three fundamental processes of evolution. They are genetic mutation, natural selection, and drift. Here I'm going to start with mutation. I've got a picture of the familiar double helix of DNA on the screen here, which is the hereditary material in humans and almost all living organisms. This is an information storage system. It's a biochemical system in a language that has an alphabet of just four letters. Not unlike our language with 26 letters, but much more efficient. The information stored in the DNA is determinant of a heritable phenotype. I need to be careful here. I do not mean full genetic determinism. It's important to remember that the environment can also affect phenotype. These phenotypic effects of the environment are not transmittable from parent to offspring. Just a quick example. Imagine an organism loses a limb at some point. It's not going to transmit that loss of limb to its offspring. When we talk about the genes or the genetic information being determinants of phenotype, we're saying it's the fraction of total phenotypic variation that can be transmitted from parents to offspring over time. We talk about the unit of that transmission of information between parents and offspring as a gene, which brings us to mutation. Mutations are thought about in the context of genes, and they are the ultimate source of heritable phenotypic variation that is subject to evolution over time.