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Lecture 8

BIOL 1201 Lecture 8: DNA Notes - pdf


Department
Biological Sciences
Course Code
BIOL 1201
Professor
Bill Wischusen
Lecture
8

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DNA:
1. Molecular Basis of Inheritance
A) What is the structure of the genome?
Genome all genetic information in the cell
Chromosome and DNA structure
All of it is really in DNA, which is part of the chromosome
B) How is the genome copied?
C) What is the genome used for?
2. DNA Structure
A) When chromosome starts to condense, replication is about to begin
B) 4 Nucleotides
C) Complementary base pairing (hydrogen bonds)
D) Double helix
E) Anti-parallel backbones (but NOT PERPENDICULAR) like the interstate and 2 lanes
Ex: DNA replication involves making ______ from DNA.
1. Protein
2. DNA
3. RNA
4. rRNA
Ex: DNA replication occurs in a ________ mechanism.
1. Liberal
2. Dispersive
3. Conservative
4. Semi-conservative
Ex: Which of the following DNA backbones is the complement to 3’
AGTCCTAC?
1. 3’ TCCAGGATG
2. 3’ AGGTAATAC
3. 5’ TCAGGATG
4. 5’ GTAGGACCT
Ex: Which of the following DNA backbones is the complement to
5CCCGGTTAT?
1. 5’ GGGCCAATA (would make them parallel)
2. 5’ GGGAATACC
3. 5’ ATAGGGACC
4. 5’ ATAACCGGG
F) Sugar and phosphate covalent bond: backbone
G) The nitrogenous bases are hanging off the backbone
H) DNA deoxyribose
I) RNA ribose
Difference: hydroxyl group instead of hydrogen
J) RNA is made of single backbone
K) DNA is made of double backbone
L) Hydrogen bonding between complementary base pairs

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3. DNA Replication
A) How is DNA copied?
B) What does the structure of DNA tell you about how to copy it?
C) Easier to separate two backbones from each other than it is to break them apart
Semi-Conservative
1. Start with single parent DNA molecule
2. Separate the two backbones
3. Each backbone now provides a template
a. We know which nucleotide to attach
4. Add the appropriate nucleotides to both backbones
5. Now there are 2 DNA replicates
Replication
1. Begins at many origins
2. Strands must separate and unwind
a. Involves:
i. Helicase responsible for unwinding
ii. Topoisomerases responsible for taking care of the
stress that has been put on molecule by unwinding it in
center
iii. SSB (single stranded binding) proteins responsible for
holding the 2 backbones apart once they’re unwound
3. Add a primer to tell replication where to start (primase)
a. We always build new strand from 5’ end to 3’ end in the
opposite direction
4. DNA polymerase is the enzyme that does the actual replication
a. Builds the new backbone from 5’ end to 3’ end and build it anti-
parallel to template it’s working on
b. Fuse sections/fragments together
i. DNA ligase
5. Ex: Leading strand DNA synthesis would occur in which locations?
a. I and IV
6. Questions:
a. What happens if the wrong base is added?
i. There are enzymes that travel along to check and make
sure the right base is there
ii. That is found and kicked out and the right base is put in
b. Where does the energy come from?
i. The nucleotides bring their own energy
c. Why does DNA polymerase only build 5’ to 3’?
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