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.
-sugar=deoxyribose

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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