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Central Dogma
DNA is the genetic material
within the nucleus.
Replication
The process of replication
creates new copies of DNA.
The process of transcription
creates an RNA using
DNA information.
DNA
Transcription
RNA
Nucleus
The process of translation
creates a protein using
RNA information.
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Translation
Protein
Cytoplasm
Transcription
• DNA is used as a template for creation
of RNA using
• the enzyme RNA polymerase.
DNA
5’
G T C A T T C G G
3’
3’
C A G T A A G C C
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5’
Transcription
• RNA polymerase reads the nucleotides
on the
• template strand from 3’ to 5’ and creates
an RNA
• Molecule in a 5’ to 3’ direction that looks
like the codingGstrand.
T C A T T C G G
C A G T A A G C C
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Transcription
• The new RNA molecule is formed by incorporating
• nucleotides that are complementary to the
template strand.
DNA coding strand
5’
DNA
G T C A T T C G G
3’
3’
G U C A U U C G G
3’
C A G T A A G C C
5’
DNA template strand
5’
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RNA
Two types of nucleic acids
•RNA
•DNA
•Usually single-stranded
•Usually double-stranded
•Has uracil as a base
•Has thymine as a base
•Ribose as the sugar
•Deoxyribose as the sugar
•Carries protein-encoding
information
•Carries RNA-encoding
information
•Can be catalytic
•Not catalytic
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Two types of nucleic acids
# of strands
kind of sugar
bases used
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rRNA is part of ribosome, used to translate
mRNA into protein
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tRNA is a connection between anticodon and
amino acid
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Initiation of transcription
Transcription begins at the 3’ end of the gene in a
region called the promoter.
The promoter recruits TATA protein,
a DNA binding protein, which in turn recruits
other proteins.
TATA binding protein
Promoter
DNA
GG
Transcription factor
Gene sequence
to be transcribed
TATA CCC
TATA box
Transcription begins
When a complete transcription complex is formed
RNA polymerase binds and transcription begins.
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
10.10 Eukaryotic RNA is processed before leaving
the nucleus
• Noncoding
segments called
introns are
spliced out
Exon Intron
Exon
Intron
Exon
DNA
Cap
RNA
transcript
with cap
and tail
• A cap and a tail
are added to
the ends to
protect against
degradation in
the cytoplasm
Transcription
Addition of cap and tail
Introns removed
Tail
Exons spliced together
mRNA
Coding sequence
NUCLEUS
CYTOPLASM
Figure 10.10
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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Fig. 10.20
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10.8 The genetic code is the Rosetta stone of life
• Virtually all
organisms
share the same
genetic code
• All organisms
use the same 20
aa
• Each codon
specifies a
particular aa
Figure 10.8A
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10.8 The genetic code is the Rosetta stone of life
• Three codons do
not code from an
aa
• Rather they are
found at the end
of the coding
sequence
• Tell a ribosome
to stop
translation and
release the
protein
Figure 10.8A
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• Tryptophan and
Methionine have
only 1 codon each
• All the rest have
more than one
• AUG has a dual
function
• 3 stop codons that
code for
termination of
protein synthesis
• Redundancy in the
code but no
ambiguity
Figure 10.8A
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Translation
• The process of reading the RNA sequence of an
mRNA and creating the amino acid sequence of a
protein is called translation.
DNA
Transcription
T
T
C
A
G
T
C
A
G
A
A
G
U
C
A
G
U
C
DNA
template
strand
Messenger
RNA
mRNA
Codon
Codon
Codon
Translation
Protein
Lysine
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Serine
Valine
Polypeptide
(amino acid
sequence)
10.11 Transfer RNA molecules serve as
interpreters during translation
• In the cytoplasm,
a ribosome
attaches to the
mRNA and
translates its
message into a
polypeptide
• The process is
aided by transfer
RNAs
Amino acid attachment site
Hydrogen bond
RNA polynucleotide chain
Anticodon
Figure 10.11A
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A codon of three nucleotides determines choice of
amino acid
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Translation is composed of three steps
• Initiation
translation begins at start codon
(AUG=methionine)
Elongation
the ribosome uses the tRNA
anticodon to match codons to
amino acids and adds those amino
acids to the growing peptide chain
Termination
translation ends at the stop codon
UAA, UAG or UGA
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• mRNA, a specific tRNA, and the
ribosome subunits assemble during
initiation
Large
Ribosomal
subunit
Initiator tRNA
P site
A site
Start
codon
mRNA binding site
Small ribosomal
subunit
1
Figure 10.13B
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2
Translation initiation
Leader
sequence
Small ribosomal subunit
5’
3’
mRNA
mRNA
U U C G U C A U G G G A U G U A A G C G A A
U A C
Assembling to
begin translation
Initiator tRNA
Met
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Translation Elongation
Ribosome
5’
3’
mRNA
A U G G G A U G U A A G C G A
U A C C C U
tRNA
P
A
Amino acid
Met
Gly
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Large ribosomal subunit
Translation Elongation
5’
3’
mRNA
A U G G G A U G U A A G C G A
U A C C C U
A
A C
A
P
Met
Gly
Cys
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Translation Elongation
5’
3’
mRNA
A U G G G A U G U A A G C G A
P
C
C
U
A C A U U C
Cys
Gly
Lengthening
polypeptide
(amino acid chain)
Me
t
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Lys
A
Translation Elongation
Stop codon
5’
mRNA
A U G G G A U G U A A G C G A U A A
C
U U C G C U
A
A
A
P
Cy s
Gly
et
M
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Lys
Arg
Release
factor
Translation Termination
Stop codon
Ribosome reaches stop codon
5’
mRNA
A U G G G A U G U A A G C G A U A A
G C U
U
P
U
C
Release
factor
Arg
Lys
Met
Gly
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Cys
A
Translation Termination
Once stop codon is reached,
elements disassemble.
A U G G
GA UG U
AA G C
G A U
A A
G C
P
U
Release
factor
A rg
s
Cy
Met
Gly
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s
Ly
A
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Levels of protein structure
Primary structure
Secondary structure
Tertiary structure
sequence of amino
acids
shapes formed with
regions of the protein
(helices, coil, sheets)
shape of entire folded
protein due to interactions
between particular peptides
Quaternary structure
structures formed by
interaction of several proteins
together
e.g. Functional hemoglobin is
two alpha-hemoglobin proteins and
two beta-hemoglobin proteins
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Levels of protein structure
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Misfolding of protein impairs function
•Misfolded prion protein disrupts functions of other
normally folded prion proteins.
•Aberrant conformation can passed on propagating like
an “infectious” agent.
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