tRNA and Codon-Anticodon Recognition Flashcards
List the three types of RNA that play major roles in translation.
- mRNA
- rRNA
- tRNA
What is the function of mRNA?
Codes for proteins
What is the function of tRNA?
serve as adapters between mRNA and amino acids during protein synthesis.
What is the function of rRNA?
form core of ribosome’s structure and catalyze protein synthesis
What is the function of miRNA?
Regulate gene expression.
How do tRNA molecules carry out their adapter function?
Carry a specific amino acid, recognizes specific codon, matches amino acid to codon.
What does the anticodon loop of tRNA do?
Recognizes codon
What does the 3’ end of tRNA do? WHat is its conserved sequence?
Covalently binds to amino acid; CCA
How long is tRNA on average?
75 nucleotides.
What are the five modified bases in tRNA?
N,N-dimethyl G, dihydro U, pseudouridine, 4-thiouridine, inosine.
What is the purpose of tRNA having modified bases?
Helps with codon-anticodon recognition.
Where does tRNA interact with mRNA?
Within the confines of the ribosome.
Why is the anticodon said to be the reverse complement to the codon?
Complimentary to sequence of codon and written in reversed order
Explain wobble pairing in tRNA.
Codon positions 1 and 2 pair with anticoding following Watson-Crick rules. Codon 3 base pairing can wobble, accepting unconventional base pairing.
What can U wobble pair to in eukaryotes and prokaryotes?
A, G, or I for both.
What can C wobble pair to in eukaryotes and prokaryotes?
G or I for both
What can A wobble pair to in eukaryotes and prokaryotes?
P: U or I
E: U
What can G wobble pair to in eukaryotes and prokaryotes?
P: C or U
E: C
Which enzyme catalyzes tRNA charging?
Aminoacyl tRNA synthetases
What is aminoacyl-tRNA?
tRNA charged with an amino acid
How many aminoacyl-tRNA synthetases are there?
20; one for each amino acid
How does the aminoacyl-tRNA synthetase charged the tRNA with an amino acid?
Covalently links carboxy end of amino acid to 3’-OH of 3’ A of tRNA.
What is a class I aminoacylt-tRNA synthetase?
Amino acylation at 2’-OH of tRNA adenine. Amino acid then transferred to 3’ OH.
What is a class II aminoacyl-tRNA synthetase?
Amino acylation directly at 3’-OH.
What is the 2 step reaction in tRNA charging?
- Amino acid covalently linked to ATP, generating aa-AMP
- Amino acid transferred from aa-AMP to 3’ adenine of tRNA
What are the two sites aaRS uses to selectively attach/remove amino acids?
- Synthesis site
- Editing site
What is the role of the synthesis site in aaRS?
Amino acids that are too large cannot enter. Anything of the correct size or smaller gets added.
What is the role of the editing site in aaRS?
Correct amino acid cannot enter the editing site. Incorrect ones enter and get cleaved off.