07b: Protein Synthesis Flashcards
How many bases in tRNA for euk? And prok?
Same for both: 75 bases
What percent of bases in tRNA are base paired?
50%
(X)% of bases in tRNA are modified.
X = 10
All tRNA molecules have which base sequence at the (5’/3’) end?
CCA at 3’ end
Where on (X) molecule is the site of AA charging?
X = tRNA
at 3’ end
Which loops are present in tRNA?
- D loop
- Anticodon loop
- T loop
Function of tRNA D loop
Recognized by synthetase enzymes
Function of tRNA T loop
Interacts with 5S rRNA (helps position tRNA in ribosome)
The (X) sequence always present at the (3’/5’) end of tRNA is (transcribed/added post-transcriptionally).
X = CCA
3’ end
Either encoded or added post-transcriptionally
The 3D structure of tRNA shows that it has which shape?
L-shape
(Prok/euk) tRNA are multimeric, which means:
Prokaryotic; 2 or more tRNA per transcript
T/F: Bacterial tRNA transcripts may be embedded in rRNA transcripts.
True
Steps to Bacterial tRNA transcript processing:
- RNases cleave 5’ then 3’ ends
- Bases modified
- CCA added to 3’ end
(Prok/euk) tRNA are monomeric, which means:
Eukaryotic;
Only 1 tRNA per transcript
What are the key differences, if any, between euk and prok tRNA?
- Euk monomeric precursor and prok multimeric
2. Intron in anticodon loop of euk tRNA
What’s the reason for the (intron/exon) in the (X) loop of (prok/euk) tRNA?
Intron
X = anticodon
Eukaryotic
So that tRNA precursor can’t be used in protein synthesis prematurely
Removal of tRNA (X) in anticodon loop, activating the tRNA, involves:
X = intron
- Endonuclease cleavage
- ATP-dependent ligation
How many precursors does it take to synthesize all 3 bacterial rRNAs?
One large precursor
Describe the processing of bacterial rRNA from precursor.
RNase III cleaves double-stranded regions of RNA in an asymmetric manner (leaving 2 base 3’ overhang)
Euk rRNA synthesis is done by:
RNA Polymerase I
Eukaryotic rRNA precursors are transcribed from (highly/moderately/single)-repetitive sequences.
Moderately
Is there post-transcriptional processing of eukaryotic rRNA?
Yes - self-splicing of 45S rRNA precursor
T/F: All euk rRNA are transcribed by the same protein.
False - 5S rRNA transcribed by RNA Pol III (rest by Pol I)
Where does transcription of 5S rRNA take place?
Nucleus
Where does transcription of most euk rRNA take place?
nucleolus (except 5S rRNA)
Where does assembly of the individual ribosomal subunits take place in euk?
Nucleolus (5S rRNA and ribosomal proteins go into there to assemble)
What are the organelles of protein synthesis?
Ribosomes
List the characteristics of the genetic code.
- Degenerate
- Non-ambiguous
- Almost universal (except mitochondria)
Genetic code is degenerate means:
more than 1 codon for some AAs
Genetic code is non-ambiguous means:
only 1 AA for each codon
A point mutation is:
single base change
A silent mutation is:
Change that specifies the same AA
Missense mutation is:
Change that specific different AA
Nonsent mutation is:
Change that produces STOP codon
Which changes can cause frameshift?
Addition/deletion of 1 or 2 bases
The anticodon on (X) interacts with codon on (Y) in (Z) fashion
X = tRNA Y = mRNA Z = antiparallel
The sequences of (codons/anticodons) are given 5’ to 3’.
Both!
What’s the sequence of the anticodon that would base pair with codon UCA?
UGA
Wobble indicates flexibility with:
3’ Base Codon
According to wobble, (X) can base pair with a number of different (Y).
X = 5' base anticodon Y = 3' base codon
