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Biology 1002B Study Guide - Quiz Guide: Dna Ligase, Endonuclease, Dna Gyrase

Course Code
BIOL 1002B
Tom Haffie
Study Guide

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Organizing DNA
-DNA has length of 2m and compacted into small nucleus
-Must be able to unwind and still be usable
-DNA wrapped around histone proteins→ Forms nucleosome→ Linkers binds with
nucleosomes→ Compacts Nucleosomes→ Creates solenoid→ Solenoid coiled→ Forms
Dogma of molecular biology:
-DNA can be replicated, transcribed and translated
-(owever, events are unidirectional from DNA→ RNA→ Protein
*Transcription does not require replication
Models of DNA Replication
-DNA must be replicated when cell divides so daughter cells each have a copy of genetic
-Three possible models: Conservative, semi-conservative, dispersive
-Conservative: One copy had 2 strands of parental DNA, the other had no parental
-Dispersive: Both copies have dispersed segments of parental DNA.
-Semi-conservative: Both copies are half new, half parental
-Watson and Crick theorized replication was semi-conservative but had no proof
-Meselson and Stahl: Proved DNA replication was semi-conservative
-Used non-radioactive nitrogen isotope, 15N to tag parental DNA.
-Cultured e.coli in medium of 15N
-15N incorporated into nitrogenous base of DNA, labelling it.
-Transferred bacteria to culture containing lighter 14N isotopes
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