Chapter 11 - Mutation

Following with the discussion on mutagens, we took on chemicals that cause mutations through a variety of mechanisms (base analogs, nucleotide-altering chemicals, and chemicals that bind to DNA).  We provided examples on their mechanism of action and on how they may affect the phenotype.

Then we discussed types of mutations at the nucleotide sequence level.  We described the three main categories: nucleotide substitutions, insertion/deletions (indels), and allelic expansions (a.k.a dynamic mutations).  We explained how they happen, when they alter the phenotype, and when and why they can be considered (or not) frameshift mutations.

We mentioned the mechanisms that cells have in place to fight off mutations (proofreading mechanism and repair systems) but details will be considered next week.

On Monday:  Exam 2...!

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Chapter 11 - Mutation

Today we continued the chapter on mutation, discussing how to find the origin of a mutation in a sex-linked gene.  We also talked about how calculate mutation rates in humans, when they are visible  in the phenotype.  We defined the conditions under which such calculation is possible.

We mentioned factors that determine variation in mutation rate in different genes and factors that increase such rate. We introduced the concept of radiation as a mutagen and started describing the most common sources of it and mechanisms of action.

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Lab 08 - 'Classic' population genetics

Screenshot of PopCycle, by John Herron
(click on pic for full size image)
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Today we did the "classic" population genetics lab. "Classic" as opposed to the increasingly strong trend of studying population genetics based on the coalescent theory.

We introduced concepts that are key to the study of population genetics such as allele frequency, genotype frequency, gene pool, and Hardy-Weinberg principle (and equilibrium) and its assumptions. When discussing the Hardy-Weinberg principle we discussed the forces that can alter allele frequency in a population: genetic drift, selection (including sexual selection), mutation, and migration.

We then then proceeded to further study Hardy-Weinberg equilibrium by running simulations on PopCycle, a software package created by Jon Herron, from the University of Washington. PopCycle allowed us to see the conditions under which allele and genotype frequencies remain constant, and it also allow us to relax some of the assumptions. We introduced the effect of genetic drift and natural selection. Students were able to observe their effect on allele frequency

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