SNC 4UDATE: ________________________
Translation
Translation Overview
Synthesis of proteins in the cytoplasm
Involves the following:
1.mRNA (codons)
2.tRNA (anticodons)
3.ribosomes
4.amino acids
Messenger RNA (mRNA)
_______________ the information for a specific protein
Made up of __________ to __________ nucleotides long
Sequence of 3 bases called codon
______ methionine or ___________________
__________________________ _________________
Transfer RNA (tRNA)
Made up of 75 to 80 nucleotides long; single stranded
Role _________________________________________________
At one end, picks up the appropriate _______________ floating in the cytoplasm
At the other end, has ________________ that are _______________________ to mRNA codons
Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds
E.g. if mRNA codon is AUA, anticodon is _______ and carries __________________
The Wobble Hypothesis
The _______________ in each codon may differ between two codons that code for the same amino acid
E.g. UAU and UAC both code for _________________
The tRNA with anticodon AUA can still bond to ________
Flexibility helps with possible errors made during _________________________
The Ribosome
Made of a ________ and __________ subunit
Composed of _______ (40%) and ____________ (60%)
Bind to mRNA at _________
_________________ of translation
Have two sites for tRNA attachment
P ___________________
A ___________________
move along mRNA in ___________ direction
_____________ is added each time a ribosome reads a codon
Reading frame
The phase in which to read the mRNA as groups of three
Possible problem
If ribosome doesnt start reading at the appropriate nucleotide, it could affect the polypeptide sequence
E.g. AUGCCAGAU... can have the following reading frames:
AUG CCA GAU... or UGC CAG AU...
It depends on where the ____________ begins ________________
Therefore, it is important that the mRNA be positioned properly
Translation
Three steps:
1. initiation: start codon (AUG)
2. elongation: amino acids linked
3. termination: stop codon (UAG, UAA, or UGA)
Initiation
Start codon (_______) is recognized by ribosome
Ensures correct reading frame
AUG codes for __________________
tRNA carrying methionine enters _________ (official initiation)
Elongation
The next ______ carrying the appropriate amino acid enters the _____
First amino acid bonds to second amino acid via _____________
Ribosome shifts (translocates) one ______________
tRNA in P site _____________ and is recycled
Now tRNA that was attached to A site is moved to ____________
3rd amino acid enters the now available ____________ and bonds to 2nd amino acid via peptide bond
Process continues until _______________ is reached
Termination
Ribosome reaches ____________________ (UGA, UAG, UAA)
Dont code for a.a., so no incoming tRNAs; process stops
Release factor
Recognizes process stopping
Aids in ___________ of ____________________________ from ribosome
Two ribosome subunits fall off mRNA; translation officially finished
____________________________ of protein is made
Homework
Page 254 # 1a-c, 2-4, 6, 7, 9
53
mRNA
A
U
G
C
U
A
C
U
U
C
G
1
-
tRNA
2
-
tRNA
U
A
C
G
aa1
aa2
A
U
A
peptide bond
3
-
tRNA
G
A
A
aa3
Ribosomes move over one codon
(leaves)
53
mRNA
A
U
G
C
U
A
C
U
U
C
G
1-tRNA
2-tRNA
U
A
C
G
aa1
aa2
A
U
A
peptide bond
3-tRNA
G
A
A
aa3
Ribosomes move over one codon
(leaves)
53
59
mRNA
A
C
A
U
G
U
aa1
aa2
U
primary
structure
of a protein
aa3
200
-
tRNA
aa4
U
A
G
aa5
C
U
aa200
aa199
terminator
or stop
codon
Termination
59
mRNA
A
C
A
U
G
U
aa1
aa2
U
primary
structure
of a protein
aa3
200-tRNA
aa4
U
A
G
aa5
C
U
aa200
aa199
terminator
or stop
codon
Termination
59