Which of the following is not true of tRNA molecules?
A) The 3'-terminal sequence is -CCA.
B) Their anticodons are complementary to the triplet codon in the mRNA.
C) They contain more than four different bases.
D) They contain several short regions of double helix.
E) With the right enzyme, any given tRNA molecule will accept any of the 20 amino acids.
2. Match the factor or enzyme at the right with the stage(s) of protein synthesis at which it acts. If a factor or enzyme participates in two stages of protein synthesis, indicate both of them.
___ Amino acid activation
(a) RF1
___ Initiation
(b) EF-Tu
___ Elongation
(c) Aminoacyl-tRNA
___ Termination
(d) Shine-Dalgarno sequence
3. Indicate whether each of the following statements is true (T) or false (F).
___ Bacterial mRNA is broken down within a few minutes of its formation in E. coli.
___ Bacterial mRNA consists only of the bases that code for amino acids.
___ Polysomes do not necessarily contain mRNA.
___ Bacterial mRNA normally occurs as a double-stranded structure, with one strand containing codons, the other containing anticodons.
___ Bacterial mRNA can be translated while it is still being synthesized.
4. Briefly explain (a) why there is a lag in cell growth when bacteria are switched from a medium containing glucose to one containing lactose. (b) When the growth medium contains both lactose and glucose, what proteins will be bound to the lac operon regulatory region? (c) If only lactose is in the growth medium, what proteins will be bound to the lac operon regulatory region?