Biology 1002B Lecture Notes - Lecture 13: Reactive Oxygen Species, Southern Blot, Nuclear Dna

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The endosymbiosis theory aims to explain the endomembrane system, which we
think occurred from the in-folding of the plasma membrane of an ancestral
We think mitochondria are descended from aerobic bacteria
A subset of those who took up the mitochondria also took up some cyanobacterium
which gave them chloroplasts
Evidence for endosymbiosis
o Morphology tells us that mitochondria look very much like aerobic bacteria
and chloroplasts look a lot like cyanobacteria
o Formation/division chloroplasts and mitochondria are not coded for by
genes, it divides as if it was a separate cell (their division apparatus is
homologous to the bacterial division apparatus), they undergo binary fission
They have their own genomes which allows them to divide and make
all of the necessary proteins they need
They have everything they need to convert DNA into something that is
needed by the cell like mRNA and tRNA
o Lateral/horizontal gene transfer over millions of years, some
mitochondria/chloroplast genes have moved to the nucleus
***I lateral gee trasfer, you’e oly haged the loatio of the
geeti iforatio, ut it’s futio/hat it odes for has ot
this raises some issues that we will discuss later
we can detect lateral gene transfer through a southern blot (DNA)
you look for a probe that encodes for a mitochondria enzyme
if you pick up a copy in the mitochondria DNA but find it in the nuclear
DNA it shows that lateral gene transfer has occurred
how lateral gene transfer occurs is that the organelle makes a copy of
the gee, seds it to the uleus, akes sure it’s orkig, the
degrades its own copy
if your southern blot shows a copy in both the mitochondria and
uleus, e’e aught the orgaelle i the at ad it has’t degraded
its own copy yet
if we only find a copy in mitochondria and not nucleus it means that
lateral gene transfer has not occurred yet
why would you move genes anyway?
o Reactive oxygen species (ROS) make reactive oxygen which are strong
oxidizing agents that can oxidize and damage DNA
o The solution is to get your DNA away from ROS
o Wait, ut this is’t all!
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