Unit 3 Lecture 10/26

2. Properties of DNA
a. Supercoiled
i. Coiled upon itself several times
ii. Clustered up in a bunch
b. Double-stranded with antiparallel strands
i. Strands are pointed in opposite directions
ii. DNA: sugar-phosphate backbone attached to bases
1. Is what is holding the bases in the order they are in
2. They are facing in an opposite direction (picture in notebook)

c. Complementary base-pairing semiconservative replication
i. For every round of DNA replication one strand is brand new and the other one is recycled from the template strand
ii. One strand is always recycled (picture in notebook)

3. Steps of DNA replication (DRAW PICTURES!) bacteria replication
a. oriC: Where DNA replication beigns on the bacterial chromosome
i. bacteria chromosome is circular and before division is supercoiled on itself
ii. first bacteria must be unwound/uncoiled and unzipped somewhere on the DNA but cannot uncoil the entire chromosome; only a small part of it
iii. this unwinding and unzipping on part of the DNA is at the oriC site
iv. oriC  origin of chromosome replication; where the replication of the chromosome is going to start
1. has a lot of As & Ts little Gs & Cs at it because this is the sequence of bases that is the easiest to unzip because they only have a double hydrogen bond
2. Enzymes bind to the DNA here
a. DNA A  not made out of DNA it is a protein enzyme that binds to oriC site on DNA
i. Brings in another protein DNA B
b. DNA B helicase  enzyme that uncoils the DNA supercoils
b. DNA B Helicase uncoils supercoils around ori C
i. unzips DNA double strands
ii. Primase  enzyme that synthesizes a small swatch of RNA that is complementary to part of the oriC sequence/DNA sequence
1. Primease attaches to unzipped DNA, synthesizes RNA primer
2. Primase synthesizes a little primer swatch of RNA complementary to DNA at oriC (picture in notes)

c. DNA polymerase attaches to the RNA primer, synthesizes DNA
i. DNA polymerase enzyme is going to bring in bases that are complementary to the bases on the single strand of DNA (template strand) and match them up and hook the bases together using a sugar phosphate backbone
ii. This enzyme can only move/travel in a 5’ to a 3’ direction

Unless otherwise stated, the content of this page is licensed under Creative Commons Attribution-ShareAlike 3.0 License