RNA Translation Flashcards
What makes Aminoacyl-tRNA synthetase a special enzyme
2nd Enzyme to have its own editing function. !st is DNA polymerase
Ribosyme
RNA melecules that have enzyme activity
How many nucleotides code for 1 amino acids
3
How many combinations of nucleotides triplets are there
64
How many of the total triplet combination of nucleotides are stop codons
3
How many sense codons are there
61
Other name of stop codons
non sense codon
How many nucleotides are in a codon
3 nucleotides
What are the three nucleotides that make up the antisense codon
Uracil and Purine nucleotide
Which combination of Uracil and Purine nucleotides is not considered a stop codon
UGG(Tryptophan)
Which amino acids have only 1 codon that codes for it
Methionine and tryptophan
What provides the framework for the second statement of
the Central Dogma (RNA specifies Protein).
Translation
What do we need for protein synthesis?
1) Ribosome
2) Aminoacyl-tRNAs
3) mRNA
4) Soluble protein factors
Wgich soluble protein factors have GTPase activity
IF-2
EF-Tu and EF-G
RF-3
Why do some soluble protein factors have GTPase activity
In translation, they act as GTP fueled
motors to drive the process of protein
synthesis forward.
Usually Eukaryotic mRNA are polycistronic
False theyre monocistronic
‘What does it mean for Eukaryotic mRNA to be monocistronic
It means it codes for only 1 polypeptide
What is the start codon in Eukaryotic mRNA
AUG
What are some of the covalently modify nucleotides present in tRNA
Pseudouridine
Dihydrouridine
The first two nucleotide can vary without affecting the amino acids. true or false?
False, the first two nucleotides must always be constant, else would lead to mutation
Which position nucleotide in a codon can vary without affect the amino acid
The 3rd nucleotide
Give three characteristics of the Genetic Code:
- its a ribonucleotide “triplets”.
- its “degenerate
- its “universal”.
What does it mean for genetic code to be degenrate
Most amino acids are specified by more than 1 codon
What does it mean for genetic code to be universal
And whats its exception
It codes for the same amino acids in every organism
The only exceptionis in mitochondria
point mutation,
Silent mutation
mis sense mutations,
nonsense mutations,
read through mutations
Insertion or deletion mutations,
Splicing mutation
Chromosomal Abnormalities
Which amino acids have 6 genetic codes that specifies them
Agenine leucine Serine
What are the two parts of
Small Subunit
Large Subunit
30s 50s together 70s
Which tRNAs identify the first codon for methionine both in Eukaryotes and Prokaryotes
fMet-tRNA for bacteria
And Met-tRNA i for Eukaryotes
Initiatiation occurs at what part of the ribosome
Small subunit
The peptidyl transferase reaction occurs in what subunit of the ribosome
50S subunit(Large subunit)
What specific species of the 50s Subunit cata;yzes the peptidyl transferase reaction
The 23s species
What are the 3 Ribosome binding sites
A site for Aminoacyl-tRNA
p for peptidyl-tRNA
E for exit
Movement of ribosome one codon at a time
Translocation
Aminoacyl-tRNA binding to A site
Elongation factor TU
Translocation
Elongation factor G in prokaryotes
All tNRA have what at the 3’ end
CCA
About 20% of the bases in trna are covalently modified
Aminoacyl-tRNA synthas
Adds the correct amino acid to the correct tRNA
How is the anino acid attached tp trna
3’ and 2’
Which position is prefered by the ribosome
3’end
Two purposes of tRNA aminoacylation
(tRNA “charging”)
:
1)
Provides the amino acid with the
necessary “adaptor”
2)
Activates the carboxyl group for
peptide bond formation
There
The ribosome is a ribozyme
Terminates protein synthesis
puromycin
Peptidyl transferase reaction is in the large subunit
What locates the start codon methionine sometimes in prokaryotes
fMet-tRNA
What locates the start codon methionine in eukaryotes
Met-tRNA
In Prokaryotes
Shine-Dalgarno sequence
Rich in purine nucleic acids, Forms complementary base pair with the 3’ end of 16S base pair to help identify the start and also holds the mRNA in place
Kozak Sequence
CCAUGG complementary CCAUGG
Palindromic sequence
A dna squence which is equal to their complementary base pair
Why are prokaryotes mRNA polycistronic
Because of the Shine-Dalgarno sequence
In Prokaryotes
what is also known as the dissociating factor
Initiation factor 3
In Prokaryotes
What does IF 3 do
Seperates the small subunit
What role does IF-2 play in translation
It binds to the fmet-tRNA and positions it at the p-site
Where does IF-1 bind during initiation in Translation
At the A site
WHat causes the release of the initiation factors from the small sub unit of the ribosome
The gtpase of IF-2, converting GTP from GDP releasing the factor
WHat is the order of binding by the initiation factors
IF 3 then IF 1 then IF2
In Prokaryotes
What is the function of EF tu
binds aminoacyl tRNA to the A site
In Prokaryotes
What is the function of EFts
replaces GDP with GTP on EFtu
In Prokaryotes
What is the function of EF-G
Promotes translocation by GTPase
In Prokaryotes
What is the Most abundant protein in bacteria
EF Tu
What are the equivalents of the elongation factors in prokaryotes in Eukaryotes
eEF1a- EFTu
eEF1b-EFts
eEF2- EF-g
Eukaryotic Translation initiation
1)
Binding of the
mRNA cap by the 40S
subunit+initiation
factors
2) Scanning of the
mRNA to search
for AUG
3) Binding of the
60S subunit
Name one way by which gene expression is regulated during translation
By the binding of the 4E-BP( Binding Protein) which is a competitive inhibitor
Phosphorylation causes the release of the 4E-BP
phosphorylation of eIF2
translation regulation, Phosphorylation blocks eIF
2B
catalyzed release of GDP
40S subunit binds cap with eIF complex and then scans the mRNA until it finds the 1st AUG. Requires:
➤met-tRNA Met ➤ helicases (to unwind 2º structure in mRNA) ➤ ATP
How many releasing factors are present in Eukaryotes
In Eukaryotes theres only one releasing factor that identifies all the stop codons
3 termination codons
UAG recognized by RF
1 (36 kD)
UAA
UGA
recognized by RF 2 (38 kD )
RF
3 releases bound RF 1 or 2;
(46 kD) requires GTP
Translation immediately follows transcription in eukaryotes, Why?
Because theres no need to pre process the mRNA by splicing and capping
