Notes March 30

Chapter 6: DNA Replication
A.) DNA replication is semi-conservative: One of the replicated strands is new each time. (per round of DNA replication ,only 1/2 of DNA molecule is new; old strand is the template stand.) This is a consequence of complementary base-pairing , double-strandedness of DNA.

B.) Stuff needed for DNA replication:
1.)Original DNA molecule (template strand); original strand of DNA to be copied.
2.) Pool of nucleotide triphosphates: ATP, GTP, CTP, TTP.
ex: Adenine-P-P-P (Bases in DNA attached to each other via sugar-phosphate backbone.) By breaking phosphates off ATP, GTP, etc., will provide the energy for the synthesis of sugar phosphate backbone.
3.) DNA polymerase(enzyme): A multi-subunit enzyme that synthesizes new DNA strand by pairing nucleotide triphosphate bases, then forming phosphodiester bond between bases in newly-synthesized strand. (ex: Taq polymerase: used in PCR reactions)
4.) DNA helicase(eukaryotes)/DNA gyrase(prokaryotes): Enzyme that will unwind our DNA.
5.) RNA primers: DNA polymerases can't copy single-strands of DNA without a swatch of double-strandedness to attach to. A small strand of RNA complementary to swatch of DNA.
-They do not degrade as quickly, so our cells do not use them. It is where the primer is bound no DNA synthesis until after the primer.

C.) Eukaryotes: Linear chromosomes. Always initiated; initiation of replication starts at the ends of chromosomes. Ends of eukaryotic chromosome: telomeres(shortening of telomeres helps turn on signals that lead to cell suicide and decrease of chaperones.
Prokaryotes: Circular chromosomes

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