Download Translation PPT

Warmup 11/12


Differentiate a codon and an anitcodon.
Which do you use to read the following
chart?
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From Gene
to Protein
How Genes
Work
AP Biology
5/23/2017
Translation
from
nucleic acid language
to
amino acid language
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5/23/2017
How does mRNA code for proteins?
DNA
TACGCACATTTACGTACGCGG
4 ATCG
mRNA
4 AUCG
protein
AUGCGUGUAAAUGCAUGCGCC
?
Met Arg Val Asn Ala Cys Ala
20
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How can you code for 20 amino acids
with only 4 nucleotide bases (A,U,G,C)?
mRNA codes for proteins in triplets
DNA
TACGCACATTTACGTACGCGG
codon
mRNA
AUGCGUGUAAAUGCAUGCGCC
?
protein
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Met Arg Val Asn Ala Cys Ala
The code

Code for ALL life!


strongest support for
a common origin for
all life
Code is redundant


several codons for
each amino acid
3rd base “wobble”

Start codon
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
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AUG
methionine
Stop codons

UGA, UAA, UAG
a
a
From gene to protein
nucleus
cytoplasm
transcription
DNA
a
a
translation
mRNA
a
a
a
a
a
a
a
a
a
a
a
protein
a
a
a
a
a
a
a
ribosome
aa
trait
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Transfer RNA structure

“Clover leaf” structure
anticodon on “clover leaf” end
 amino acid attached on 3 end

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Loading tRNA

Aminoacyl tRNA synthetase


enzyme which bonds amino acid to tRNA
bond requires energy

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ATP  AMP
bond is unstable
so it can release amino acid at ribosome easily
Trp C=O
OH
OH
Trp C=O
O
Trp
H2O
O
activating
enzyme
tRNATrp
anticodon
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tryptophan attached
to tRNATrp
AC C
UGG
mRNA
tRNATrp binds to UGG
condon of mRNA
Ribosomes

Facilitate coupling of
tRNA anticodon to
mRNA codon


organelle or enzyme?
Structure
ribosomal RNA (rRNA) & proteins
 2 subunits

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large
small
E P A
Ribosomes

A site (aminoacyl-tRNA site)


P site (peptidyl-tRNA site)


holds tRNA carrying next amino acid to
be added to chain
holds tRNA carrying growing
polypeptide chain
Met
E site (exit site)

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empty tRNA
leaves ribosome
from exit site
U A C
A U G
5'
E
P
A
3'
Building a polypeptide

Initiation


Elongation


brings together mRNA, ribosome
subunits, initiator tRNA
adding amino acids based on
codon sequence
Termination

3 2 1
end codon
Leu
Val
Met
Met
Met
Met Leu
Ala
Leu
Leu
release
factor
Ser
Trp
tRNA
U AC
5'
C UGAA U
mRNA A U G
3'
E P A
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5'
UAC GAC
A U G C U GAA U
5'
3'
U A C GA C
A U G C U G AAU
5'
3'
U AC G A C
AA U
AU G C U G
3'
A CC
U GG U A A
3'
Destinations:
Protein targeting
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Signal peptide
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address label

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start of a secretory pathway
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
secretion
nucleus
mitochondria
chloroplasts
cell membrane
cytoplasm
etc…
RNA polymerase
DNA
Can you tell
the story?
amino
acids
exon
intron
tRNA
pre-mRNA
5' GTP cap
mature mRNA
aminoacyl tRNA
synthetase
poly-A tail
large ribosomal subunit
polypeptide
5'
small ribosomal subunit
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tRNA
E P A
ribosome
3'
Bacterial chromosome
Protein
Synthesis in
Prokaryotes
Transcription
mRNA
Psssst…
no nucleus!
Cell
membrane
Cell wall
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5/23/2017
Prokaryote vs. Eukaryote genes

Prokaryotes

Eukaryotes

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DNA in cytoplasm
circular
chromosome
naked DNA

no introns

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DNA in nucleus
linear
chromosomes
DNA wound on
histone proteins
introns vs. exons
introns
come out!
intron = noncoding (inbetween) sequence
eukaryotic
DNA
exon = coding (expressed) sequence
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Translation: prokaryotes vs. eukaryotes

Differences between prokaryotes &
eukaryotes

time & physical separation between
processes


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takes eukaryote ~1 hour
from DNA to protein
no RNA processing

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Translation