Microbiology, 2021

11 • Review Questions 463
46. ________ is a group of mechanisms that allow
for the introduction of genetic material from
one organism to another organism within the
same generation.
47. The DNA sequence, to which repressors may
bind, that lies between the promoter and the
first structural gene is called the ________.
Short Answer
49. Can two observably different cells have the
same genotype? Explain.
50. Why is primase required for DNA replication?
51. What is the role of single-stranded binding
protein in DNA replication?
52. Below is a DNA sequence. Envision that this is a
section of a DNA molecule that has separated in
preparation for replication, so you are only
seeing one DNA strand. Construct the
complementary DNA sequence (indicating 5’
and 3’ ends).
DNA sequence: 3’-T A C T G A C T G A C G A T
C-5’
53. What is the purpose of RNA processing in
eukaryotes? Why don’t prokaryotes require
similar processing?
54. Below is a DNA sequence. Envision that this is a
section of a DNA molecule that has separated in
preparation for transcription, so you are only
seeing the antisense strand. Construct the
mRNA sequence transcribed from this
template.
Antisense DNA strand: 3’-T A C T G A C T G A C
G A T C-5’
55. Why does translation terminate when the
ribosome reaches a stop codon? What happens?
Critical Thinking
63. A pure culture of an unknown bacterium was
streaked onto plates of a variety of media. You
notice that the colony morphology is strikingly
different on plates of minimal media with
glucose compared to that seen on trypticase soy
agar plates. How can you explain these
differences in colony morphology?
64. Review Figure 11.4 and Figure 11.5. Why was it
important that Meselson and Stahl continue
their experiment to at least two rounds of
replication after isotopic labeling of the starting
DNA with 15 N, instead of stopping the
experiment after only one round of replication?
48. The prevention of expression of operons
encoding substrate use pathways for substrates
other than glucose when glucose is present is
called _______.
56. How does the process of translation differ
between prokaryotes and eukaryotes?
57. What is meant by the genetic code being nearly
universal?
58. Below is an antisense DNA sequence. Translate
the mRNA molecule synthesized using the
genetic code, recording the resulting amino acid
sequence, indicating the N and C termini.
Antisense DNA strand: 3’-T A C T G A C T G A C
G A T C-5’
59. Why is it more likely that insertions or deletions
will be more detrimental to a cell than point
mutations?
60. Briefly describe two ways in which
chromosomal DNA from a donor cell may be
transferred to a recipient cell during the
process of conjugation.
61. Describe what happens when a nonsense
mutation is introduced into the gene encoding
transposase within a transposon.
62. What are two ways that bacteria can influence
the transcription of multiple different operons
simultaneously in response to a particular
environmental condition?
65. If deoxyribonucleotides that lack the 3’-OH
groups are added during the replication
process, what do you expect will occur?
66. Predict the effect of an alteration in the
sequence of nucleotides in the –35 region of a
bacterial promoter.