DNA & RNA Lecture II
Using the Code of Life
DNA & RNA
1
Two process involve DNA
1. Replication: making an exact copy of DNA
 purpose: reproduction
 occurs: nucleus
 uses: only DNA
2. Protein Synthesis: production of proteins
 purpose: growth & reproduction
 occurs: between nucleus & ribosomes
 uses: both DNA & RNA
2
Replication
Making Exact Copies of DNA
3
DNA Unzip
4
Replication of Helix
5
Mechanism of Replication Basics
6
Replication
• Creates an exact copy DNA
• Steps:
1. DNA unzips
2. “Free-floating” nucleotides
in cytoplasm fill slots along
existing strand of DNA
3. Two double strands formed.
7
Replication
• A more detailed diagram.
8
Comparing DNA & RNA
DNA
• Double stranded
• Deoxyribose Sugar
• Phosphate
• Nitrogenous bases
–
–
–
–
Adenine
Cytosine
Thymine
Guanine
RNA
• Single stranded
• Ribose Sugar
• Phosphate
• Nitrogenous bases
–
–
–
–
Adenine
Cytosine
Uracil
Guanine
9
Protein Synthesis
10
Why Do We Need Proteins?
1. Cell Structure
• Cell = 80% protein
Cell membrane
11
Why Do We Need Proteins?
2. Cell Processes
• Hormones (signals)
• Enzymes (speed up reactions)
12
Why Do We Need Proteins?
3. Membrane Channels (remember
transport?)
4. Neurotransmitters
(carry nerve/brain
messages)
13
What Do We Need For
Protein Synthesis?
1. DNA
 Template for making
mRNA during
Transcription
14
What Do We Need For
Protein Synthesis?
2. RNA
a) mRNA — messenger RNA
makes & takes copy of
DNA to cytoplasm.
b) tRNA — transfer RNA
Matches w/ mRNA on
ribosome. Carries AA to
add to protein chain.
15
What Do We Need For
Protein Synthesis?
3. Ribosome
Reads mRNA
Directs tRNA
Creates peptide bonds between AAs
makes polypeptide (protein) chain
16
What Do We Need For
Protein Synthesis?
4. Amino Acids (AAs)
• Building blocks of
proteins (20 AAs
exist)
• Protein = AA chain =
polypeptide chain
• ORDER MATTERS!
AA order determines
function of protein
17
Amino Acids
18
Steps of Protein Synthesis
1. Transcription (writing the “message”)
DNA makes mRNA
 messenger carries code to
cytoplasm
2. Translation (reading the “message”)
mRNA and tRNA make protein (AA chain)

message translated into a protein
19
Steps of Protein Synthesis
20
Steps of Protein Synthesis
(Nucleus)
(Cytoplasm)
21
Transcription
Transferring the DNA Code to mRNA
DNA to mRNA
22
Transcription — Basics
23
Transcription
DNA to mRNA
Location = nucleus
1. Enzyme binds to DNA, unzips it
2. mRNA makes a copy of gene from DNA
template
*U replaces T in RNA
24
Transcription
3. A codon is a threeletter “word” of
instruction
4. Codons are made
of mRNA
25
Transcription
5. They attach to
anticodons at
ribosomes
6. Anticodons are
attached to clover
leaf like structures
which carry a
specific amino
acid.
26
Transcription
5. DNA nucleotides (triplet) turn
into mRNA codon
Codons
27
Transcription
28
Translation
Writing the Code to form Amino Acids
(Proteins)
mRNA to tRNA
29
Translation
Decoding (writing) — bonding of amino
acids to form proteins
mRNA and tRNA make protein (AA chain)
Location = cytoplasm
30
Translation — Basic
31
Translation
Steps of Translation
1. mRNA moves to
cytoplasm, binds to
ribosome
2. tRNA anticodon
brings AA (amino
acid) to mRNA
codon on ribosome
32
Translation
3. Ribosome
moves down mRNA to next codon
4. tRNA anticodon picks up & attaches next AA
with peptide bond
33
Translation
5.
tRNA leaves ribosome once AA attached
Protein chain
AA
tRNA
mRNA
34
Translation
6. Steps
1-5 repeated, adding Aas until STOP
CODON signals end of protein
7. Polypeptide chain (protein) released from
ribosome
35
Translation
36
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
GGA
CCT
TAT
ACT
37
Synthesis Practice
DNA
Triplet
mRNA
Codon
TAC
AUG
tRNA
Anti-codon
GGA
CCT
TAT
ACT
38
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCT
TAT
ACT
39
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
CCT
TAT
ACT
40
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
TAT
ACT
41
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
TAT
ACT
42
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
CCU
TAT
ACT
43
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
CCU
TAT
AUA
ACT
44
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
CCU
TAT
AUA
UAU
ACT
45
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
CCU
TAT
AUA
UAU
ACT
UGA
46
Synthesis Practice
DNA
Triplet
mRNA
Codon
tRNA
Anti-codon
TAC
AUG
UAC
GGA
CCU
GGA
CCT
GGA
CCU
TAT
AUA
UAU
ACT
UGA
ACU
47
AMINO ACID FUN!!






DNA Triplet: ACC
mRNA codon: UGG
tRNA anti-codon: ACC
Amino acid: Tryptophan
Why you sh
Tryptophan is in TURKEY – makes you sleepy
48
Protein Synthesis
49
Protein Synthesis Animation
http://www.columbia.edu/cu/biology/course
s/c2005/images/animtransln.gif
50
List of Condons & Amino Acids
51
List of Amino Acids
52