22. W hy is the error rate (incorporation of the wrong amino acid) of translatio

Question

22. W hy is the error rate (incorporation of the wrong amino acid) of translation low? A. Specificity of base pairing between codons and anticodons. B. Specific binding of aminoacyl tRNA synthases to amino acids. C. Proof reading by the ribosome. D. The ribosome only uses GTP, not ATP, for energy E. A and B are true. 23. The anticodon for wild-type tyrosine tRNA base pairs with UAU and UAC codons on the mRNA. A mutant tyrosine tRNA also base pairs with the UAA codon. It also binds the tyrosine aminoacyl tRNA synthase. Using the table showing the genetic code, what effect would this mutation likely have on translation? A. There would be no effect on translation. B. Proteins shorter (fewer amino acids) than normal produced C. Proteins longer (more amino acids) than normal produced D. No proteins would be synthesized. E. Tyrosine would be incorporated instead of cysteine. UCCUAC UAA Stop UGA Stop A UAG Stop UGG TrpG CCG CAG CGG ACC AAC ACAAAAL AGA GUA CCA GAA GGA 24. The coding sequence for a mRNA is 5'-AUG UUU AAA UGA-3' IMMEDIATELY after forming the FIRST peptide bond what molecule is covalently bound to the tRNA in the A-site of the ribosome? Use the table showing the genetic code, (-represents the covalent bond to the tRNA). A. an uncharged -tRNA B. MET-tRNA c. PHE-MET-RNA. D. MET-PHERNA E. LYS-PHE-MET-tRNA 25. When a codon in a mRNA is 5-ACG-3', what is the sequence of the tRNA anti-codon? A. 5-ACG-3 B. 5-UGC 3 C. 5'-GCA-3 D. 5-CGU-3 E. 5-CGA-3

Explanation / Answer

22. B. specific binding of aminoacyl tRNA synthase to amino acids.

Specific binding of aminoacyl tRNA synthase to amino acids is responsible for the occurence of low error rate (less than 1 in 1, 00, 000). The base pairining between codon and anticodons is the weak point for the low error rate.

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