chapeter 6 note

DNA replication

I. DNA replication is semmi-conservative
- per round of DNA replication, only 1/2 of DNA molecule is new. this is a consequence of complementary base-pairing, double-standedeness of DNA.
old strand = template strand

II. stuff needed for DNA replication
1. original DNA molecule (template strand)
2. pool of nucleotide triphosphates = ATP, GTP, CTP, TTP = breaking phosphates off these nucleotide triphosphates provides energy for synthesis of sugar phosphate backbone. the bases in DNA are attached to each other by this sugar phosphate backbone.

3. DNA polymerase = multi subunit enzyme that synthesize new DNA strand by pairing nucleotide - TP to template bases, then forming phosphodiester bond between bases in newly synthesized strand. ex: tag polymerase

4. DNA helicase/ DNA gyrase = enzyme that unwinds DNA bc DNA is supercoils, need to unzip the strands
5. RNA primer = small strand of RNA complementary to swatch of DNA.
DNA polymerase cant single strand of DNA w/o a little swatch of double strandededness attach.

We use DNA primer b/c its more stable than RNA primer

III. steps of DNA replication

a. Initiation
i. ori sites
1. prokaryotes = circular chromosome
2. eckaryotes = linear chromosome. initiation of replication starts at ends of chromosome among other places.
end of eukaryotes chromosome = telomeres —> shortening of telomerses lead to cell suicide.

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