Class Notes (834,979)
Canada (508,839)
Biology (6,794)
Lecture 17

Biology 2581B Lecture 17: Mechanisms of Genome Evolution

2 Pages
99 Views
Unlock Document

Department
Biology
Course
Biology 2581B
Professor
L.Graham Smith
Semester
Winter

Description
Lecture 17: Mechanisms of Genome Evolution - What do we talk about when we talk about genome evolution? o Differences in genome architecture: size, structure, content, modifications ▪ There’s huge diversity in genome architecture: within cells, within lineages, and between different lineages – how do we explain this diversity? o Forces responsible for differences - Think about genome evolution at a molecular level: the level at which mutations occur in genes - The only way to get different genome architecture is through mutation o Different levels of mutations: type, context, frequency, bias 1) Type - Includes point mutations: T-A site changes to C-G site - Deletion, insertion, large insertions/deletions, duplications, rearrangements, fragmentation, fusion, conversion (one sequence basically copies itself onto another sequence) o Large insertions can occur through HGT, mobile elements, endosymbiotic gene transfer 2) Context: where is it occurring? Is it occurring in non-coding DNA? If so, is it regulatory? - Is it happening to a region, or to the whole genome? - Is it impacting the whole cell? 3) Frequency: does it happen often or rarely? - Often you get a system where you have many point mutations, and very few fragmentation events, or vice versa 4) Bias - One type of point mutation could be more frequent than another type – mutational spectrum Mutations alter genomes - Mutations are a reflection of the environment the cell lives in - The actual cellular machinery that we have could alter genomes as well - Some organisms have really good DNA maintenance machinery – this is pretty rare o This means you hardly get any mutations (e.g. plant mitochondrial genomes) - Sometimes you have a really crappy DNA maintenance machinery – more common o Doesn’t work well, always inserting mutations (e.g. animal mitochondrial genomes) Thinking about evolution - Evolution is a population-level process - The little white things in the image are algae - Let’s add a mutation into the population, so we’ve changed the genome of one of these organisms - When this happens, we could get one of two outcomes - Over time, this change will either get fixed in the population, or lost - What determines whether a mutation will get fixed or lost? - First question: is the mutation beneficial, deleterious, or neutral? o If beneficial, you’d want to have it fixed - Next question: is this population effectively large or small? o “effectively” because you can have huge populations that behave like small populations o what determines this is the probability that a member can pass on its genes to its offspring o If population is selectively large, natural selection is efficient - If you have many competitors, a little mutation that’s beneficial can give you an advantage - In tiny populations, natural selection sucks o E.g. remember the woolly mammoth example,
More Less

Related notes for Biology 2581B

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit