TRANSLATION:

1

• TRANSLATION
• THE PROCESS OF CONVERTING GENES INTO PROTEINS

Suggested Reading 2nd Chapter 13, pp. 333-367 3rd
Chapter 13, pp. 324-355
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THE OBJECTIVES OF THIS SECTION ARE

• Focus on the key features of translation
• The genetic code
• Transfer RNA
• Ribosomes
• Focus on the translation process

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Proteins
2nd Figure 13-13 3rd Figure 13-15
2nd Figure 13-13 3rd Figure 13-15
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Proteins
Review protein structures
Review protein chemistry
Review amino acids
2nd Figure 13.6 3rd Figure 13.8
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So, how does one convert DNA information into
protein structures?
The key is in the genetic code!
Both editions
But, there is more to this than just a table of
codes!!
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COLINEARITY OF GENE AND PROTEIN
Both editions Figure 13-2
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3
COOH
NH3
A mess!!! And this would be lethal, like a
genetic disease!!!
No fig in new text
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Codes in the RNA transcript
5 GAC GGU UUU GGG CCC GCG GAA CAA CUG 3
3 CTG CCA AAA CCC GGG CGC CTT GTT GAC 5
DNA template
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(5 GAC GGU UUU GGG CCC GCG GAA CAA CUG 3)
Codes in the RNA transcript
5 GAC GGU UU G GGC CCG CGG AAC AAC UG 3
3 CTG CCA AA C CCG GGC GCC TTG TTG AC 5
DNA template
(3 CTG CCA AAA CCC GGG CGC CTT GTT GAC 5)
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THE GENETIC CODE TABLE
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THE GENETIC CODE AND ITS FEATURES

• The codes or codons are________________
• A ___________(a change of one nucleotide to
  another nucleotide) would therefore
  _________________amino acid
• 2) Triplet codons
• Three bases/nucleotides per codon, hence per
  amino acid
• 3) Codes for all 20 amino acids

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• 4) Most of the amino acids are coded by gt1 codon,
  some with as many as 6 codons
• gtgtThe codons are _________for some amino acids
• 5) The common ____________(amino acid) is ATG
  (methionine)
• 6) There are 3 ________________codons
• 7) The codes are read from a fixed starting point
  and continues in triplets until the end of the
  coding sequence

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TRANSFER RNA THE INFORMATION CONVERTER
2nd Figure 13-10 3rd Figure 13-12
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TRANSFER RNA THE INFORMATION CONVERTER
SUMMARY OF KEY FEATURES

• Each tRNA has a special _____________________to
  its assigned amino acid
• The assigned amino acid is..
• These enzymes are called ________________________
  ________

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Charging tRNA with aminoacyl-tRNA synthetase
2nd Figure 13-11 3rd Figure 13-13
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• The assigned amino acid is linked
• via the _______________________site
• (3OH-ACC)

• The anticodon loop contains the
• anticodon triplet sequence
• The anticodon is ________________________________
  __in the mRNA
• Some of the anticodons have ________
• in its ability to bind to the 3rd position of
• a codon, a phenomenon called _______

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Other useful structural features that provide
specificity

• TFC Loop and the DHU Loop both are
• involved in ribosome binding
• ____________Helix
• Extra arm of variable lengths
• The _________ _________Arm

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What is the driving force for precise
translation?
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2nd Figure 13.12a 2rd Figure 13.14a
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THE GENETIC CODE TABLE
gtgt Nonoverlapping
gtgtFor 20 amino acids
Triplets
Stop codons
Multiple codons for one amino acid
Start codon
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2nd Figure 13-12b 3rd Figure 13-14b
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Codons for serine can be serviced by different
tRNAs
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Ribosome The Protein Maker
What are the key features that make this process
work?
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Review Ribosome Composition
rRNA
Proteins
Subunits
Assembled ribosomes
2nd Figure 13-13 3rd Figure 13-15
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Purpose of the ribosomal components?
2nd Figure 13-13 3rd Figure 13-15
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Ribosome The Translation Machinery
2nd Figure 13-14c 3rd Figure 13-16c
What is happening at the A site?
What is happening at the P site?
What is happening at the E site?
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Summary of Key Ribosome Features

• 1) Consists of rRNAs and proteins
• 2) The rRNAs and proteins form two subunits
• large and small, and these two form the
• ribosome
• 3) There are three sites involved in the
• translation process
• A site the ___________site for incoming
• charged tRNA
• P site the __________ site for the growing
• protein chain
• E site the _____site for discharged tRNA

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The Translation Process

• Can be divided into three main stages
• Initiation (How to start correctly and where)
• Elongation (Code name for continuation)
• Termination (Where to stop)

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(No Transcript)
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Initiation (How to start correctly and where)
2nd Figure 13-16 3rd Figure 13-18
All factors steps are to ensure alignment
order
Question What would happen if there was no
alignment or orderliness?
Question What would happen if
translation starts incorrectly?
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Initiation (How to start correctly and where)
Specialized Initiator Factor, IF3
P site
2nd Figure 13-16 3rd Figure 13-18
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Initiation (How to start correctly and where)
Specialized Initiator Factor, IF2
All factors steps are to ensure alignment
order
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Initiation (How to start correctly and where)
5 UTR
2nd Figure 13-17 3rd Figure 13-19
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Elongation (Code name for continuation)
All factors steps are to ensure alignment
order
2nd Figure 13.18 3rd Figure 13.20
Cycles
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Termination (Where to stop)
Stop Codon Encountered
3UTR
Release Factor 1 with no amino acid
Question What would happen if translation was
terminated incorrectly?
Cleavage disassembly
2nd Figure 13.19 3rd Figure 13.21
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Translation A summary
INITIATION

• Requires mRNA, ribosomes, charged tRNAs,
  initiation factors (IF), and a _____________ tRNA
• The initiator tRNA __________ carries
  N-formylmethionine
• This is for the start codon AUG on the mRNA

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ELONGATION

• A cyclical process
• Requires several elongation factors (EF) and GTP
  (energy)

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• Requires release factors (RF) that recognize stop
  codons (UAA, UAG, UGA)

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What does it look like all together, especially
in prokaryotic systems?
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3
DNA
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3
3
5 UTR
5 UTR
5 UTR
5 UTR
30S FACTORS
INITIATE
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