Chapter 15

Which of the following statements about the initiation phase of translation is false? a. An initiation factor allows \(5^{\prime}\) mRNA to attach to the small ribosomal subunit. b. Initiation factors complex with GTP to help Met-tRNA and AUG pair. c. mRNA attaches first to the small ribosomal subunit. d. GTP is synthesized. e. \(3^{\prime}-\mathrm{UAC}-5^{\prime}\) on the tRNA binds \(5^{\prime}-\mathrm{AUG}-3^{\prime}\) on \(\mathrm{mRNA}\).

Which item binds to SRP receptor and to the signal sequence to guide a newly synthesized protein to be secreted to its proper "channel"? a. ribosome b. signal recognition particle c. endoplasmic reticulum d. signal peptidase e receptor protein

A missense mutation cannot be: a. the code for the sickle-cell gene. b. caused by a frameshift. c. the deletion of a base in a coding sequence. d. the addition of two bases in a coding sequence. e. the same as a silent mutation.

Which of the following is not correct about transposable elements? a. They can be recognized by their ends of inverted transposable elements. b. They have an internal portion that can be transcribed. c. They encode a transposase enzyme. d. They have no harmful effects on cell function. e. They move by a cut-and-paste or copy-and-paste mechanism.

1\( causes phenylalanine to build up. b. A mutation for enzyme #2 prevents tyrosine fro… # Which statement about the following pathway is false? a. A mutation for enzyme \)\\# 1\( causes phenylalanine to build up. b. A mutation for enzyme #2 prevents tyrosine from being synthesized. c. A mutation at enzyme \)\\# 3\( prevents homogentisic acid from being synthesized. d. A mutation for enzyme \)\Rightarrow 2$ could hide a mutation in enzyme 4 e. Each step in a pathway such as this is catalyzed by an enzyme, which is coded by a gene.

A part of an mRNA molecule with the sequence \(5^{\prime}\) -UGC GCA-3 is being translated by a ribosome. The following activated tRNA molecules are available. tRNA Anticodon \(3^{\prime}-\mathrm{GGC}-5^{\prime}\) \(3^{\prime}-\mathrm{CGU}-5^{\prime}\) \(3^{\prime}-\mathrm{UGC}-5^{\prime}\) \(3^{\prime}-\mathrm{CCG}-5^{\prime}\) \(3^{\prime}-\mathrm{ACG}-5^{\prime}\) \(3^{\prime}-\mathrm{CGG}-5^{\prime}\) Amino Acid Proline Alanine 'Treonine Glycine Cysteine Alanine Which two of them can bind correctly to the mRNA so that a dipeptide can form? a. cysteine-alanine b. proline-cysteine c. glycine-cysteine d. alanine-alanine e. threonine-glycine

Which do you think are more important to the accuracy by which amino acids are linked into proteins: nucleic acids or enzymatic proteins? Why?