L16 Genetic Variation Interactive notes_Fall 2020.docx -...

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Mutation and Genetic Variation Genotype and Phenotype Types of Mutations The Nature of Mutations Small Scale vs. Large Scale Mutations Almost all species have a lot of genetic variation . Genetic variation is important because it: Accounts for individual variation Accounts for biodiversity of species So, genetic variation spans a huge scale, from the individual to the species level on a global scale. Genetic variation is generated by mutations . What is meant by the term heritable and why is it an important aspect of mutations? Heritable means that the mutation is stable and therefore passed on through cell division. It is important because it is the main source for genetic variation Sometimes mutations are perceived as being negative or harmful but many mutations have no effect and some are actually beneficial. Beneficial mutations are especially important because they make evolution possible. In the human population, differences in height, weight, hair and eye colour are just a few traits that are effects of mutations. Although mutations occur in one cell at a particular time, natural selection drives whether the number of individuals in the population with that mutation increases or decreases over time. Genotype and Phenotype Before continuing, it is important to be familiar with a few terms that will be used in upcoming lectures. Please review/learn these definitions: Gene pool – All of the alleles present in all individuals in a population or species Alleles - the different forms of any gene. Alleles correspond to different DNA sequences in the genes Genotype - the genetic makeup of a cell or organism Phenotype - an individual’s observable characteristics (i.e., height, eye color, lactose intolerance, weight, color blindness, etc.) Polymorphism - Any genetic difference among individuals that is present in multiple individuals in a population. Types of Mutations Harmful mutations: Harmful mutations often affect an organisms’ ability to survive and reproduce in a particular environment. Often harmful mutations don’t persist beyond a few generations whereas less harmful mutations may persist. Why do you think this is this the case? Ppl with harmful mutations would be able to reproduce hence their line is cut short. Their mutation is not favourable to the population. Textbook reference: Chapter 14 Please work through these interactive online lecture notes before attending Lecture 17. 1
Polymorphisms for example, although they don’t directly cause a particular disease can contribute to increasing susceptibility of a disease. One example is emphysema . 1AT gene encodes the enzyme (alpha-1-antitrypsin or 1AT) that inhibits another enzyme called elastase. Elastase breaks down elastin. Study part a of the diagram below to understand the importance of elastase activity in the normal lung.

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