Chapter 15: Translation
How many amino acids are there?
20 amino acids
reading frame
3 ways in which the sequence can be read in groups of 3. Each different way of reading encodes a different amino acid sequence.
What is the first step of translation elongation?
A charged tRNA binds to the A site.
Which of the options are mechanisms of mRNA surveillance? A.) nonstop mRNA decay B.) premature‑termination mediation C.) nonsense‑mediated mRNA decay D.) tRNA mediated mRNA decay E.) no‑go decay
A.) nonstop mRNA decay C.) nonsense‑mediated mRNA decay E.) no‑go decay
Which does the termination of translation require? A.) release factors B.) terminator tRNA C.) stop codon on the mRNA D.) GTP E.) E site of the ribosomal complex
A.) release factors C.) stop codon on the mRNA D.) GTP
Which component of translation is frequently targeted by antibiotics? A.) the ribosome B.) tRNAs C.) the template mRNA D.) aminoacyl‑tRNA synthetase E.) IF‑2
A.) the ribosome
initiation codon
AUG
Which of the statements about the genetic code are most accurate? A.) The promoter sets the reading frame. B.) The genetic code is generally‑non‑overlapping. C.) An initiation codon sets the reading frame. D.) The genetic code is generally overlapping. E.) Three initiation codons set the three possible reading frames.
B.) The genetic code is generally‑non‑overlapping. C.) An initiation codon sets the reading frame.
Which of these is not involved in the initiation of translation in bacteria? A.) tRNA carrying N-formylmethionine that will occupy the P site B.) tRNA carrying the next amino acid that will occupy the A site C.) small and large ribosomal subunits D.) GTP and initiation factors E.) mRNA
B.) tRNA carrying the next amino acid that will occupy the A site
wobble
Base pairing between codon and anticodon in which there is nonstandard pairing, usually at the third (3′) position of the codon; allows more than one codon to pair with the same anticodon
There are 64 codons, 20 different amino acids, and approximately 30-50 tRNAs. Which statement does not help explain these numbers? Many amino acids are coded for by more than one of the 61 sense codons. A.) Isoaccepting tRNAs can carry the same amino acid. B.) Synonymous codons code for the same amino acid. C.) Flexibility, or wobble, between the anticodon and the codon allows one tRNA to pair with multiple codons. D.) The 3' base of the anticodon on the tRNA can pair weakly with the 5' codon base
D.) The 3' base of the anticodon on the tRNA can pair weakly with the 5' codon base
Which statement is most consistent with the one gene, one enzyme hypothesis originally proposed by Beadle and Tatum? A.) Each gene makes one enzyme but not one protein. B.) A gene can only make one enzyme in a cell cycle. C.) Every enzyme makes one gene. D.) Genes and enzymes are important. E.) Every gene encodes a separate enzyme.
E.) Every gene encodes a separate enzyme.
When mRNAs are being translated simultaneously by multiple ribosomes, the structure is known as a(n)
Polyribosomes
During the initiation of translation in bacteria, the small ribosomal subunit binds to which consensus sequence?
The Shine-Dalgarno sequence
What primarily determines the secondary and tertiary structures of a protein?
The amino acid sequence (primary structure) of the protein
Do the initiation and termination codons specify amino acids? If so, which ones?
The initiation codon in bacteria encodes N-formylmethionine; in eukaryotes, it encodes methionine. Termination codons do not specify amino acids.
Termination Codon
UAA, UAG, UGA (nonsense codon)
nonoverlapping
a single nucleotide may not be included in more than one codon
In elongation, the creation of peptide bonds between amino acids is catalyzed by a. rRNA. b. a protein in the small ribosomal subunit. c. a protein in the large ribosomal subunit. d. tRNA.
a. rRNA.
degenerate code
amino acid may be specified by more than one codon
Proteins are composed of________ linked together by__________ bonds.
amino acid; peptide
In a polyribosome, the polypeptides associated with which ribosomes will be the longest? a. Those at the 5′ end of mRNA b. Those at the 3′ end of mRNA c. Those in the middle of mRNA d. All polypeptides will be the same length.
b. Those at the 3′ end of mRNA
A codon is a. one of three nucleotides that encode an amino acid. b. three nucleotides that encode an amino acid. c. three amino acids that encode a nucleotide. d. one of four bases in DNA.
b. three nucleotides that encode an amino acid.
Amino acids bind to which part of the tRNA? a. Anticodon b. DHU arm c. 3′ end d. 5′ end
c. 3′ end
sense codons (61)
code amino acids
synonymous codons
codons that specify the same amino acid
Through wobble, a single ____________________ can pair with more than one ____________________. a. codon, anticodon b. group of three nucleotides in DNA, codon in mRNA c. tRNA, amino acid d. anticodon, codon
d. anticodon, codon
Aminoacyl‑tRNA synthetases recognize their specific amino acid by____________and recognize the tRNAs that carry it by the__________
different size, charges, and R groups ;nucleotide sequence
isoaccepting tRNAs
different tRNAs that accept the same amino acid but have different anticodons
nonsense codons (stop codons-->3 codons)
do not code for amino acids
degenerate
genetic code contains more codons than needed
The universality of the code
near universal (with some exceptions where codon usage varies slightly in different organisms)
The discovery that some proteins are composed of more than one polypeptide chain and that different polypeptide chains are encoded by separate genes became the
one gene one polypeptide hypothesis
The way that proteins fold into beta pleated sheets and alpha helices is dependent on their
primary structure
wobble hypothesis
proposed that some nonstandard pairings of bases could take place at the third position of a codon.
The bacterial transfer‑messenger RNA system
removed stalled ribosomes in Bacteria
What is the first stage of protein synthesis?
tRNA charging, in which the tRNAs bind to amino acids
