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Lecture 2

Biology 1201A Lecture Notes - Lecture 2: Single-Nucleotide Polymorphism, Wood Mouse, Melanocortin 1 Receptor

Course Code
BIOL 1201A
Jennifer Waugh

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Lecture #2
Selection and Fitness Types of Selection
Selection and Inheritance Pattern:
Inheritance pattern of alleles under selection can influence the rate of fixation – and
therefore the amount of variation in a population.
Fixation: the loss of all alleles except one
When dominant alleles are selected against there is no way to ‘hide’ or ‘shelter’ it in
phenotypes, and therefore the allele will be ‘killed off.’
When recessive alleles are selected against, they will be ‘sheltered’ from selection in
heterozygotes. These heterozygotes continually contribute that allele to their
Link to Genetics:
Beach mice are light coloured mainland, mainland mice are darker
Blending with native soil colour reduces predation
Light colour is a result of a single amino acid change in Mc1r – single nucleotide
Frequency of light allele correlates with the degree of lightness in populations
Consequences of Selection:
1. Adaptations:
Traits that increase the probability that an individual with the trait will
survive and reproduce in a given environment.
Environment specific
Doesn’t necessarily have to be physical traits  Ex. Schooling behaviours of
2. (Micro) Evolution:
Small changes in the genetic makeup of a population
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