BIO120H1 Lecture Notes - Lecture 23: Meiotic Drive, Transposable Element, Meiosis
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Lecture 23:
-some lineages evolve greater complexity
Origin of eukaryotic cell
-Originally had two bacteria –-> aerobic prokaryotethis 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
Cheatersindividuals 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 inheritancematernal 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 individualmesses with "tness of rest of
genome
(Transposable elements) Over replication:
-over replicating so that more copies are in the gametesspreading 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)