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Transcription and Translation Exam 3
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central dogma
DNA -> RNA -> Protein
Transcription
DNA to RNA (mRNA)
Stages of Transcription
1.Initiation - recognize promoter region
2.Elongation - make a RNA copy
3.Termination - split from DNA
direction of transcription
which one it copies varies but will always copy from 5' - 3' (DNA will be facing 3' to 5')
RNA processing
Bacterial mRNAs can be used immediately Eukaryotic mRNAs need to be cut and add cap and a tail
Introns- spliced
Exons- expressed
splicing
via splicesome (made of SnRNP)
rRNA and tRNA are self splicing via ribozymes
capping
guanocine* added on 5' end NEEDED for mRNA to exit the nucleus
Poly A tail
Adenine added to the 3'
Increases stability and lifespan in cytosol
Not encoded in gene sequence
codon
mRNA base triplets
template strand
DNA strand that will be turned into mRNA
Degenerate
more than one codon can specify the same amino acid
20 amino acids
1 codon 1 amino acid but 64 possible codons
translation
mRNA to protein
tRNA
clover structure (but L shaped b/c of hydrogen)
has anticodon that matches the codon
acceptor stem for amino acid binding
Aminoacyl-tRNAsynthetase
Catalyzes the attachment of amino acids to tRNA
Reactions result in tRNA with amino acid attached or charged tRNA or aminoacyl tRNA
Ribosome
ribosomal subunits (large and small) made of rRNA
ribosome shape determined by rRNA
E (Exit), P (Growing Poplypeptide), A (Acceptor), sites
Stages of Translation
1.Initiation - mRNA, first tRNA and ribosomal subunits
assemble
2.Elongation - Synthesis from start codon to stop codon
3.Termination - Complex disassembles at stop codon
releasing completed polypeptide
Bacteria
mRNA binds to small ribosomal subunit
facilitated by ribosomal-binding sequence
Start codon a few nucleotides downstream
Initiator tRNA recognizes start codon in
mRNA
Large ribosomal subunit associates
At the end, the initiator tRNA is in the
P site
wobble
3rd base in codon can be switched some and still make the same amino acid
AUG
start in eukaryotic cells
Stop codons
terminate transcription
polyribosome
translate a single mRNA simultaneously
make copies of polypeptide quickly
Targeting the Functional Protein
polypeptide is modified after translation and completed protein target specific sites in the cell
free and bound ribosomes
free ribosomes make protein that function in cytosol
bound make protein in ER that will be secreted from the cell
they can switch!
random protein info
•Polypeptide
synthesis always begins in the cytosol
•Synthesis
finishes in the cytosol unless the
polypeptide signals the ribosome to attach to the ER
•Polypeptides
destined for the ER or for secretion are marked by a signal
peptide
Author
misol
ID
253145
Card Set
Transcription and Translation Exam 3
Description
biology exam 3 final
Updated
2013-12-14T21:15:17Z
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