DNA
{ Deoxyribonucleic Acid
History
What is passed on from parents to offspring?
Protein or DNA?
DNA!
What is the structure, what does it look
like?
DNA Structure
1.Chargaff
1.Watson, Crick , Franklin and Wilkins
Chargaff Rule
Franklin and Wilkins
Model of DNA Structure
Complementary base pairing
Hydrogen Bonds
Nucleotide
Backbone
Rungs
Replication
Replication Video
Enzyme that unzips
Helicase
SSBP’s Single
Stranded Binding
Proteins
DNA had a 5’ and 3’ side
Antiparallel
5’ and 3’ ends
Only add to 3’ side of the DNA molecule
Enzyme adds Nucleotide to
the 3’ end
How does so much DNA
get copied?
- Replication Bubbles
- Replication fork
Primer
Short sequence of RNA that is needed to begin DNA synthesis
DNA Polymerases
DNA Polymerase III
• Only works by adding nucleotides to the 3’ end
of the NEW strand
• Works in 5’ 3’ direction
DNA Polymerase I
• Removes RNA from Primer and adds DNA
Ligaseattaches
Okazaki
fragments
of the
lagging
strand
“Like Glue”
DO NOW
McGraw Hill Website

http://highered.mcgrawhill.com/sites/00724373
16/student_view0/chapter14/animations.html#
Central Dogma
DNA RNA Protein
Transcription
DO NOW
1. 3 ways DNA is different
from RNA
Transcription
3 Steps
1. Initiation
2. Elongation
3. Termination
Initiation
Promoter Region- beginning of a
gene
TATA Box - part of the promoter,
upstream of the gene
- sequence of T’s and A’s
RNA Polymerase unwinds the
DNA
Elongation
- RNA Polymerase – Only
adds to the 3’ end of RNA
- Antiparallel
- Base pairing rules
- U or Uracil instead of T
- mRNA- messenger RNA
Termination
• Terminator Sequencesequence of T’s in the
DNA
• Primary RNA transcript
is released (pre-mRNA)
RNA Processing
• Primary RNA transcript( premRNA) , modified before it leaves
the nucleus
• 5’ end G Cap- modified Guanine,
tell its to go to the Ribosome
• 3’ end Poly A tail – inhibit
degradation
RNA Processing
Introns- parts of DNA that are not expressed
between exons
Exons - genes are expressed
mRNA splicing- remove the intros
- exons exit as mature RNA transcript
- expressed
Splisosome- cuts the RNA and joins the exons
Translation
3 nucleotides in the mRNA is called a codon.
Genetic Code- information
encoded in genetic material
translated into amino acid
sequences
4 x 4 x 4= 64
20 amino acids
One start and 3 stop signals
Universal
shape
Average Protein is 400 aa
avg RNA ( exons) 1200
Translation- mRNA to protein
tRNA ( transfer RNA)- transfer
amino acids to a growing
polypeptide
Anticodon- complementary to
the mRNA codon
3 steps of Translation
1. Initiation
2. Elongation
3. Termination
Translation- Initiation
Bring together mRNA, tRNA,
- ribosome ( small subunit)
- Binds the 5’ cap
- Start codon AUG – Met, Methionine
- Then the large subunit
- Antibiotics
-
Translation- Elongation
E site, P site, A site
First one tRNA P site, A site
afterwards

Termination
Translation ends when one of three
stop codons, UAA, UAG, or UGA,
enters the A site
Ribosomes separate, polypeptide
released
Mutations
Sickle Cell Anemia
http://www.dnalc.org/resources/3d/17-sickle-cell.html
438-base sequence.
Can’t Carry Oxygen
Tay Sachs
http://www.pbs.org/wgbh/nova/body/cracking-the-code-of-life.html
Inherited genetic mutation
 Gene codes for an enzyme that breaks down
fatty acids
 Build up of fatty acids in the brain


Change in the nucleotide Sequence (
letters/bases) of a gene
Base Substitution ( can be bad or silent)
2. Base Addition/ Deletion- worse
- alter group of 3
1.
Affects the PROTEIN
Mutation

Errors in DNA replication
Xray, UV light

Sometimes GOOD? How so?

Mutagens cause
Mutations