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Lecture 9

BIOL 1000 Lecture Notes - Lecture 9: Transfer Rna, Proteoglycan, Nuclear Membrane

7 pages33 viewsFall 2010

Course Code
BIOL 1000
Michael Gadsden

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Lecture 9
DNA Repair
May happen because of UV light or a Cytisine becoming Uracil by spontaneous de-amination)
o Another way is that DNA Polymerase accidentally inserts U into DNA (as DUTP [instead
of DTTP])
Note: Many chemotherapeutic drugs affect the cell so that it increases the
amount of DUTP
WHY? If DUTP [] is increased by drugs, increase level of U in DNA there is a high
degree of repair
The repair system is then overwhelmed and this leads to DNA
fragmentation and then death of the cell
This process targets fast dividing cells (Cancer, hair etc.) and that’s why
cancer patients are bald
Excision Repair
o Remove misinserted base
I.E. via Uracil-DNA-glycosylase
o Enzyme removes a small gap of nucleotides
This is like when RNA Primase is has to be removed
o Fill in gap by DNA Poly
Proofreading by DNA Polymerase
o Enzyme will notice that there is not good H bonding and it will reverse, splice and repair
the base
o Note: Retrovirus polymerases are highly mutagenic
Repair Mechanisms:
o DNA Polmerases
Mismatch Repair
o Repair enzymes recognise mispaired base
o Enzymes remove multiple bases
o DNA Poly repairs bases
o Ligase combines two sets together
DNA contained in nucleus... etc.
o Generally something that is membrane encased and has a particular function
Ribosome is NOT and organelle because it is not membrane bound
o Compartments in a cell with a specific function (usually metabolic)
o With a degree of permanence
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Endomembrane Nucleus
o Connection found in the ER membrane (pores) and many folds
Plant Vs. Animal Cells
o Generally same thing
o Vacuole and Cell wall in Plant
Rough and Smooth ER
o Rough covered in Ribosomes so that the RNA can be quickly translated into prioteins
o Smooth synthesize fatty acids and alcohol
Liver cells have many of these because detoxification occurs in the liver
Golgi Apparatus
o Processes and packages proteins, lipids and other molecules
o Stores nutrients
o Retains and degrades waste
o Provides support
o Where particles are degraded in the cell
o Degrade and recycle materials
o Very acidic and thus if it bursts, the enzymes won’t work
Note: acid helps degrade
Tay-Sachs Disease
o Untreatable genetic disorder
Cannot degrade gangliosides Lipids + sugars
See Sheet
Ganglioside is found in high [] on nervous tissue membranes
All DNA in nucleoid
Essentially the ideology is that the nuclear envelope got two very similar membranes
Mitochondria came in (aerobic bacteria) and they became part of the cell
o For some reason, the mitochondria wasn’t eaten and it gained an evolutionary
o Host cell offers protection, and the mitochondria provides ability to aerobically respire
Photosynthetic Bacteria followed the same process and became chloroplasts
Viewing some cells allow us to believe this process
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