Bio 418 – Advanced Evolution
Week 1 Study Guide
Lecture Topics
(1) sources of variation
(2) selection 1: molecular evolution
(3) selection 2: quantitative trait evolution
Review:
Hardy-Weinberg equilibrium; how to predict genotype frequencies from allele frequencies
Four postulates of Darwinian evolution by natural selection, as modified under the Modern
Synthesis
Definition of a quantitative trait
Study questions and topics:
Define: allele, evolution, natural selection, transversion, transition, locus, purifying selection
What are the major sources of genetic polymorphism in a population?
What kinds of mutation(s) usually causes no change to the protein product of a gene? (we
discussed at least 3)
What mutation(s) change the protein product of a gene in a way that is unlikely to alter its
function?
Are transitions or transversions more likely to be observed in actual DNA sequences? Why?
Why are most substitutions in DNA sequences observed at the 3rd codon position of a gene?
Are random changes to the DNA sequence of a gene more likely to result in a synonymous or a
non-synonymous substitution? Why?
If you looked at the amino acid sequence of different alleles of a gene that plays an important
role in cell division, would you expect to see primarily synonymous or a non-synonymous
substitutions? Why?
In general, are you more likely to inherit mutations from your mother or father? Why?
Understand that mutation rates vary among genes, chromosome regions, individuals, sexes, and
species.
Explain how mutations in enhancers can cause dramatic evolution of the phenotype without
causing any change to the proteins expressed by an individual. Why is this an important source
of evolutionary novelty (meaning, new trait combinations for selection to act on)?
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Explain how mutations causing alternative splicing can similarly result in rapid changes to the
phenotype. How have such mutations contributed to the evolution of primates, including
humans?
Understand linkage. From an evolutionary perspective, why is linkage of two loci important in
sexually reproducing organisms, if one gene is under purifying selection?
What effect would purifying selection on one bacterial gene have on polymorphism at the
adjacent gene on the chromosome? What about a gene found far away on the chromosome?
What effect would purifying selection on one gene in humans have on polymorphism at the
adjacent gene (a) in over a few generations; (b) over a thousand generations? What about a gene
found far away on the same chromosome, over a few generations?
Given a graph of (a) trait values plotted versus fitness, or (b) a histogram showing change in trait
values within a population over time, be able to recognize whether a trait is under directional,
stabilizing or disruptive selection. Know how each will affect the mean versus the variance of a
trait.
Be able to write a general form of the equation for (a) directional selection, or (b) stabilizing or
disruptive selection.
Why is the same basic equation used to model stabilizing and disruptive selection? What are
these kinds of selection called, in terms of how they are modeled? How does a model for
stabilizing selection differ from the model for disruptive selection?
Explain how natural selection can act on the correlation between two traits, without acting on the
individual traits themselves. What is this called?
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