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Lecture 6

Lecture 6- Mutation

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University of Toronto St. George
Human Biology
Michelle French

Thursday, January 22, 2009 - Todays lecture is now moving into a secondpart of the course which is talking about mutation and today the mutations will be relatively small and in the next two lectures following, she will talk about how to correct mutation and the following ones will be one chromosomal abnormalities so larger changes. - So todays lecture is starting about mutation and it will be about smaller ones. - Recall that when you look at DNA and you look at its properties, there are 4 key properties that are important when you study genetics: the idea that you can store information, it can be replicated or copied, the information can be expressed and that kind of ideas and topics are what shes been talking about already especially expression. But DNA can also change and that can be useful because that change can help to drive differences amongst a species and also to drive evolution. - The different types of mutations are listed and the concept is that while we think of mutation as a bad thing, it can also be useful bc it provides variability which can then be taken up & used during evolution so there are some good & bad things about mutation. - Shown here are various types of mutations but for clarity, she has these shown on the next slides. - We studymutations a lot, she even talked about mutations in the course already without defining it in great detail bc what mutations allow us to do is to identify genes. Mutations can be markers for certain kinds of genes. - We saw that in the last time when she was talking about development, that mutations were created & we could subsequently identify certain genes involved in incorrect embryo development. That was a way to mark the genes, by mutating them we could see what would happen if something went wrong & therefore, we could study the gene itself. - Mutations can also disrupt the gene function which helps us understand how the normal or the wild type gene works When we see that a function has gone missing bc we have mutated the gene, it gives us some sense of what that gene actually does. - Wild type is the form that is mostly foundin nature or if youre look ing at a laboratory stock of animals or plants, the standard laboratory stock it is the common gene variant you have, it is the wild type & it functions normally. - A mutant is a form that has changed due mutation also known as a change due to alteration in the sequence of the DNA. It varies from the wild type. - In a forward mutation you go from the wild type to the mutant version so that is called the forward mutation. Reminder that each allele or variant of the gene is represented by a letter, sometimes the wild type also has a plus indicating that it is + the wild+type & in this example, we go from A to smaller a or you can go from a small d to a big D. The upper case means that it is dominant & the lower case means that it is recessive. - In some instances, having had these mutations happen, it is sometimes possible for the mutation to reverse back to the wild type & that is called a reverse mutation. What happens in this case is that the novel mutation reverts back to the wild type &
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