Mastering Biology 9 TRNAs| with a detailed answer key

Mastering Biology 9 TRNAs Where does translation take place? a) Endoplasmic reticulum b) Ribosome c) Golgi apparatus d) Nucleus b) Ribosome Which nucleic acid is translated to make a protein? a) DNA b) rRNA c) tRNA d) mRNA d) mRNA Which of the following processes is an example of a post-translational modification? a) Initiation b) Peptide bond formation c) Phosphorylation d) Elongation c) Phosphorylation Which of the following steps occurs last in the initiation phase of translation? a) The small subunit of the ribosome binds to the 5′ cap on the mRNA. b) The large ribosomal subunit joins the complex. c) An aminoacyl tRNA binds to the start codon. d) A peptide bond is formed between two adjacent amino acids. b) The large ribosomal subunit joins the complex. At which site do new aminoacyl tRNAs enter the ribosome during elongation? a) B-site b) A-site c) P-site d) E-site b) A-site What is meant by translocation? a) The polypeptide chain grows by one amino acid. b) The ribosome slides one codon down the mRNA. c) The two ribosomal subunits are joined in a complex. d) The completed polypeptide is released from the ribosome. b) The ribosome slides one codon down the mRNA. True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated. a) True b) False b) False What enzyme catalyzes the attachment of an amino acid to tRNA? a) aminoacyl-tRNA synthetase b) rubisco c) dextrinase d) argininosuccinate lyase e) nuclease a) aminoacyl-tRNA synthetase The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____. a) CAG b) CTG c) GAC d) CUG e) TCG d) CUG The initiator tRNA attaches at the ribosome’s _____ site. a) A b) translocation c) E d) P e) Q d) P Which one of the following is true of tRNAs? a) tRNAs are double-stranded. b) Each tRNA binds a particular amino acid. c) There are four types of tRNA. d) tRNAs carry special sequences known as codons. e) All of the above b) Each tRNA binds a particular amino acid. How is translation initiated? a) The small ribosomal subunit binds to the mRNA. b) The tRNA bearing methionine binds to the start codon. c) The large ribosomal subunit binds to the small one. d) The start codon signals the start of translation. e) All of the above. e) All of the above A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is a) UUA. b) UUU. c) AAA. d) TTT. e) either UAA or TAA, depending on first base wobble. b) UUU Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the a) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs. b) bonding of the anticodon to the codon. c) binding of ribosomes to mRNA. d) attachment of amino acids to tRNAs. e) shape of the A and P sites of ribosomes. a) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that a) the ribosome will skip a codon every time a UUU is encountered. b) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. c) none of the options will occur; the cell will recognize the error and destroy the tRNA. d) the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. e) none of the proteins in the cell will contain phenylalanine. b) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? a) an assembled ribosome with a polypeptide attached to the tRNA in the P site b) separated ribosomal subunits, a polypeptide, and free tRNA c) separated ribosomal subunits with a polypeptide attached to the tRNA d) a cell with fewer ribosomes e) an assembled ribosome with a separated polypeptide a) an assembled ribosome with a polypeptide attached to the tRNA in the P site Use the following information to answer the question.A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) in the ribosome already. Where does tRNA #2 move to after this bonding of lysine to the polypeptide? a) A site b) exit tunnel c) E site d) directly to the cytosol e) P site c) E site