06_Ribosome Assembly and Protein Synthesis Flashcards
How many frames are in each DNA strand?
3
What is an open reading frame?
A region in the sequence of DNA that potentially encodes a protein
How are rRNA genes arranged in a ribosomal gene cluster?
in tandem
What are nontranscribed spacers?
sequences that separate transcription units in a ribosomal gene cluster
Which arm of tRNA accepts amino acids?
Amino acid acceptor arm (3’ end)
Which arm of the tRNA has unusual bases?
the T arm
How does a tRNA recognize a codon sequence?
The anticodon on a tRNA complements the codon of the mRNA.
What is the enzyme that adds an amino acid to tRNA? What is the energy source used? Which end (5’ or 3’) of tRNA is the amino acid added to?
aminoacyl tRNA synthetase
ATP hydrolysis
3’ end
What is the wobble interaction in tRNA?
The nucleotide at the 5’ end of the tRNA anticodon can pair with more than one nucleotide at the 3’ end of the mRNA anticodon (3rd position)
What is the wobble base pairing permitted with each of the following in the 5’ position of an anticodon?
G, A, U, I, C
G: U or C A: U U: A or G I: A, U, or C C: G
Which nucleotides in the wobble position of a tRNA anticodon can only base pair with one type of nucleotide on the mRNA codon?
A and C
What is inosine? How does it compare to guanine?
it is a purine base most commonly found in tRNA; it is similar to guanine but is missing an -NH2.
What are the three main steps of translation?
Initiation, Elongation, Termination
Which sequence in prokaryotic mRNA guides the positioning of the small ribosomal subunit?
Shine-Delgarno sequence
Which ribosomal subunit binds to prokaryotic mRNA first?
30S small ribosomal subunit
What is the sequence of the initiation codon?
AUG
Which initiation factors are necessary for the binding of the 30S ribosome to the prokaryotic mRNA initiation codon?
IF1 and IF3
What is the tRNA in prokaryotes that recognizes the initiation codon?
formylmethionyl-tRNA
Which initiation factor is required for association of formylmethionyl-tRNA with the initiation complex?
IF2-GTP
How is IF2-GTP converted to its inactive form? How is it released from the complex?
Hydrolysis of the GTP to GDP+Pi by IF2 converts it to IF2-GDP and releases it from the complex.
This is an energetically-expensive, intrinsic activity.
What are the A, P and E sites?
A: Aminoacyl-tRNA
P: Peptidyl-tRNA
E: Exit site
