BIOL10005 Lecture Notes - Lecture 17: Intron, Cell Membrane, Nuclear Membrane
29 Jun 2018
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LECTURE 17: Diversity of kingdoms:
Prokaryotes are older than eukaryotes:
Endosymbiosis: Eukaryotes evolved from capturing of bacterium --> mitochondria
Evolution of eukaryotic cells:
oNuclear membrace
oEndomembrane system
oComplexity of genome (increased size)
Bacteria (binary fission):
oOne origin of replication --> limits generation time --> lengthy
oOutcompeted by faster replicators
oCannot have multiple origins due to multiple catenation
Converting circular chromosome to linear:
oAllows for multiple origin
oLoses ends b/c DNA synthesis start w/ RNA
oGets shorter every time
TELOMERES
oContinuously add some DNA (non-coding) to the end of the chromosome to
compensate for it being shortened each time
oEssentially, the tie a bit of sacrificial DNA onto the ends that the RNA primer can
attach to and then later be deleted without losing the crucial genes (program) in the
middle of the chromosome
oMust be present for linear chromosomes
Solve end problem
Linear chromo can have multiple origin
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Document Summary
Endosymbiosis: eukaryotes evolved from capturing of bacterium --> mitochondria. Evolution of eukaryotic cells: nuclear membrace o o. Bacteria (binary fission): one origin of replication --> limits generation time --> lengthy, outcompeted by faster replicators o. Cannot have multiple origins due to multiple catenation. Converting circular chromosome to linear: allows for multiple origin o. Loses ends b/c dna synthesis start w/ rna: gets shorter every time. Continuously add some dna (non-coding) to the end of the chromosome to compensate for it being shortened each time o. Increased genome but still replicate same time: get shorter as cells age o o. Cloned animals have short telomeres like the mature cells they are cloned from. Cancer cells have regained long telomeres which allows them to grow and divide rapidly. Nuclear membrane: er evolved by internalization of plasma membrane. Nuclear envelope: rer pressed against dna o.
