BIOL 111 Lecture Notes - Lecture 5: Exponential Growth, Directional Selection, Genetic Drift

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BIOL 111: EVOLUTIONARY PROCESSES
Mutations; beco m e the sourc e of variation nd evolution prece d e said proces s, they are what
the selection in environ m e n t s (ex: muta t e d toad, eyes in mouth)
Mutations: ULTIMATE SOURCE OF GENETIC VARIATION
-No mutation s no gen etic differentiatio n, they are chan ge s in the
gen etic cod e that gen er a t e new alleles, altering gene expression and
sometim e s some of the m will NOT have any structur al effect, the
amino acid sequ enc e s may chan g e and could have phen otypic effects
(ex: Drosophila flies)
Negative Mutations: Most muta tion s decreas e FITNESS (i.e., survival and reproductive
succ es s) and are considere d delet eriou s
-*Mutations nor mally have negativ e effects, you can det er mi n e this
through mut ation accu m ula tion & com pare/con trast the control line up
(the avg. mu tation reduc es fitnes s by 2%*
Positive Mutations: “Hopeful Monsters chance that theyll be unlikely to
occur but are of hug e effect
-Likely to be a small affect in the pheno ty p e , ben eficial to the
environ m e n t (e.g. eye sight, running spee d, mating succ es sion)
Genetic drift: random changes in allele frequency, random mortality effects, evolutionary
change (divide the # of certain alleles/total # alleles) if there is death; new # of certain alleles/
new total of alleles
-Gen etic drift is strong er in smaller populations , the chance event s are
also more import an t
-Larger populatio n still have sourc es of chang e d allele frequ e nc y, it
tak es LONGER becaus e the chan g es from gen eration to gener a tion are
smaller but even tu ally it will fix for one allele or the other
ex: Drosop hila mel ano g a s t e r (fruit fly) teste d for eye colours from the
wild type and the bw 75”, an evolutionary process that happened
overtime (has no effect in the environment)
oAs the generations move forward, the populations are
accustomed to fix towards a certain allele until it completely
changes the frequency and fixating on a specific allele
Quantitative Genetic Variation:
-Polyge nic: Broad distribution of traits of the mean height (ex: people of
differen t height standing in a row), influenc ed by multiple gene s
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BIOL 111 Full Course Notes
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