2009 Spring Molecular Biology Exam 3
Student I.D.:
I.
Name:
Fill the blanks with short answers (Each 5 points)
1. When a tRNA is charged with the amino acid corresponding to its
anticodon, it is called (
). The amino acid is linked by an ester
bond from its carboxyl group to the 2’or 3’ hydroxyl group of the ribose of
the 3’ terminal base of the tRNA. (
) is the tRNA to which the
nascent polypeptide chain has been transferred following peptide bond
synthesis.
2. The (
) is the polypurine sequence AGGAGG centered about 10bp
before the AUG initiation codon on bacterial mRNA. It is complementary
to the sequence at the 3’ end of 16S rRNA.
3. (
) is the activity of the ribosomal 50S subunit that
synthesizes a peptide bond when an amino acid is added to a growing
peptide chain. The actual catalytic activity is a property of the rRNA.
4. (
) accounts for the abilities of a tRNA to recognize more
than one codon by unusual pairing with the third base of a codon.
5. (
) of a prophage describes its entry into the lytic cycle as a result
of destruction of the lysogenic repressor, which leads to excision of free
phage DNA from the bacterial chromosome.
6. RNA polymerase binds the PRE promoter only in the presence of (
).
2009 Spring Molecular Biology Exam 3
II. Answer the question in detail
1. Distinguish between the zinc finger and leucine zipper motifs found in
some eukaryotic transcription factors. (10 points )
2. Summarize the process of RNA interferences. (10 points )
3. What three different methods were used to help break the genetic code?
(20 points )
4. What role do the initiation factors play in protein synthesis? (10 points )
5. Examine the following figure that displays a step in the process of
translation. Label the following on this figure. (20 points )
A). 5′ and 3′ ends of the mRNA,
B). A, P, and E sites
C). Start codon, D) Place on the ribosome where release factor 1 will bind
6. A synthetic mRNA added to a cell-free protein-synthesizing system
produces a peptide with the following amino acid sequence: Met–Pro–Ile–
Ser–Ala. What would be the effect on translation if the following
components were omitted from the cell-free protein-synthesizing system?
Explain your reasoning. (30 points )
(a) Initiation factor 1, (b) Initiation factor 2, (c) Elongation factor Tu
(d) Elongation factor G, (f) Release factors, (g) ATP, (h) GTP
7.
Arrange the following components of translation in the approximate
order in which they would appear or be used during protein synthesis: (20
points )
, elongation factor Tu, 30S initiation complex, initiation factor 3, fMettRNAfMet, peptidyl transferase, elongation factor G, release factor, 70S
initiation complex,
8.
Give the elongation factors used in bacterial translation and explain the
role played by each factor in translation. (10 points )
9.
Describe three horizontal methods of genetic transfer in E. coli. (20
points )
10. Explain how an antibiotic-resistance gene and the lacZ gene can be used
as markers to determine which cells contain a particular plasmid,
respectively. (20 points )