BIO120H1 Lecture Notes - Lecture 23: Meiotic Drive, Transposable Element, Meiosis

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3 Feb 2016
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Lecture 23:
-some lineages evolve greater complexity
Origin of eukaryotic cell
-Originally had two bacteria –-> aerobic prokaryotethis gave rise to eukaryotic
cell aerobic prokaryote became mitochondria Nucleus plant cells
-genomic cooperation’s that used to work independently now work together
-traits that are good for the individual may not be good for the specie—does not
spread via selection
-
Cooperation is adaptive when:
-if you have genes that lead to helping related individuals this can evolve through
the population
Recipicol altruism  if encounter enough times, we help one another
Cheatersindividuals evolving that are out for their own "tness
Unit of inheritance: gene
Unit of selection: gene
Unit of evolution: species (according to coyne)
Unit of evolution: populations
How individual genomes stay cooperative:
Through meiosis- so mom and dad copies don’t have to sel"shly compete
-mom and dad’s copies are getting equal representation in the gametes (fair
meiosis)
-cooperation works with related cells-multicellularity
-uni parental inheritancematernal inheritance from mom this prevents
competition of the mitochondria
Cooperation break down:
Meiotic drive:
-aa has some way of becoming over represented in the gamete (cheating)
-eliminates alleles that have higher individual "tness
Drosophila:
-big S has toxin in sperm that is killing of little s so big S is going to spread and be
favoured
-big S allele causes reduced "tness for the individualmesses with "tness of rest of
genome
(Transposable elements) Over replication:
-over replicating so that more copies are in the gametesspreading their copies
without considering the bene"t/survival of the individual
-35% of our genome are transposable elements!  Genes that self-replicated
themselves (sel"sh)
Selection silences sel"sh genes (as they reduce the "tness of the individual)
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