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Lecture 11

Biology 1002B Lecture Notes - Lecture 11: General Idea, Southern Blot, Metagenomics

Course Code
BIOL 1002B
Tom Haffie

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Lecture 11B
Meaning of endosymbiosis, cyanobacteria, lateral gene transfer
oLateral gene transfer: Movement of genes from mitochondria/chloroplast to
nucleus 
Origin of endomembrane system, nuclear membrane, ER etc.
Endosymbiosis - A living organism located within the cell of another living organism
Lateral Gene Transfer refers to the relocation of genes from the mitochondria or
chloroplast to the nucleus of the cell over millions of years. This allows the nucleus to take
control of the cell rather than having an autonomous cell within the cell. Relocation of the
genes does NOT change the function of the gene .
Origin of mitochondria and chloroplasts
The mitochondria and chloroplast are derived from free living prokaryotic cells through a
process called endosymbiosis but are NOT derived from the same place as the nucleus.
The mitochondria is said to have been derived from aerobic bacterium (bacteria that can
undergo oxidative phosphorylation) after a larger primitive cell brought it in through
phagocytosis. Chloroplasts are said to have descended from cyanobacteria
Evidence supporting theory of endosymbiosis
Mitochondria and chloroplast look like cyanobacteria, they are the same size, ! have the
same features!
Formation / Division!
Division of these organelles is very similar to bacteria. What is required to make ! a new !
chloroplast? Old chloroplasts dividing into two through binary ! fission. Same!process goes
for creating new bacterium, old bacterium must ! divide, cannot simply!activate genes and
pathways. !
Electric Transport Chains!
Only chloroplast and mitochondria have these components!
Mitochondria and chloroplast have their genomes and can synthesize proteins !
Transcription / Translation machinery!
Ribosomes, tRNAs, mRNAs, every type of RNA, all the machinery required to ! convert
genetic information from genome into functional protein!
Evidence for lateral gene transfer from organelles to the nucleus
General idea about how lateral gene transfer is detected (Southern blot)
Role of cpn60 in tracing endosymbiotic and lateral gene transfer event in
Relative sizes of typical mitochondrial, chloroplast and nuclear genomes
o3000 proteins for the mitochondria to work (95% encoded by nucleus)
oOriginally, years ago mitochondria, nucleus and chloroplasts had similar genome
oNow the genome sizes of mitochondria and chloroplast have decreased and
nuclear genome has greatly increased
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