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Biology
Genetics
Translation
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Cards (17)
Translation
1.
Ribosome
decodes mRNA created during
transcription
2. Ribosome turns
mRNA
code into a
polypeptide
Codon
A chain of
3
nucleotides that encodes for a specific
amino acid
There are
20
different amino acids
The genetic code is
redundant
Start codon
AUG encodes for
methionine
(
Met
), the only
start
codon
Stop codons
UAA
UAG
UGA
Translating mRNA into protein
1. Read
codons
one at a time
2. Assemble
amino acids
in the right sequence
3. Occurs in the
5'
to
3'
direction of the mRNA
4. With the help of
transfer
RNA (tRNA)
tRNA
Folded
RNA
molecule with an
anticodon loop
complementary to the mRNA codon, carries a specific
amino acid
The
3rd
nucleotide in the anticodon is often less
important
than the first two
The
3rd
nucleotide is in the "
wobble
" position, allowing fewer tRNA to be needed
Phases of Translation
1.
Initiation
2.
Elongation
3.
Termination
Ribosome
Complex of proteins and
RNA
Has
3
binding sites for tRNA
Initiation
1.
tRNA
carrying met attaches to small
ribosomal
subunit
2. Complex binds to
mRNA
cap and travels to
start
codon
3. Binds to
large
ribosomal subunit to begin
translation
Elongation
1. tRNA matching codon binds to
A
site
Termination
1.
Stop codon
enters
A
site
2. Release factor binds and facilitates
hydrolysis
to free
polypeptide
chain
3. Complex
separates
to be reused
Post-translational modifications
Amino acids
may be removed
Polypeptide
can be divided into pieces
Multiple polypeptides can join to form larger
proteins
Polypeptides fold into 3D structure with
chaperone
proteins
Specific
amino
acid
sequences can target proteins to organelles
Polysome
Multiple ribosomes reading
the same mRNA, allowing
more protein
to be made simultaneously