Prokaryotes & Viruses
Class Work
1. What are the simplest organisms that fit the definition of life?
2. Identify one type of prokaryote that humans depend on.
3. Provide two examples of bacteria being helpful to humans.
4. What does it mean for an organism to be unicellular?
5. Most prokaryotes do not live alone, but instead live with other prokaryotes
forming _____________________.
6. Bacteria is one type of prokaryote, _______________________ is a second type.
7. The structures inside a cell are known as _____________________.
8. Describe the composition of a cell wall.
9. What are pili made of and where are they found?
10. Identify the two types of pili.
11. Identify the organelle that allows bacteria to be mobile.
Homework
12. _____________________was not considered an organism because it was not a living
thing, but it was the precursor to life.
13. List the remarkable characteristics of habitats that prokaryotes are able to
survive in.
14. Describe the size of prokaryotes.
15. List three sources that provide helpful bacteria to humans.
16. Describe the structure and shape of prokaryotes.
17. Why are archaea known as extremophiles?
18. Tell where the cell wall in a prokaryote can be found.
19. List 3 functions of the cell wall.
20. Describe the function of fimbriae.
21. Define taxis.
22. Identify and describe the 3 components of flagella.
Class Work
23. Genes are segments of ______________.
24. The specific location of a gene on a chromosome is referred to as what?
25. Describe the structure of DNA.
26. In DNA replication, thymine pairs with __________________.
27. Define codon.
28. Through what process do bacterial cells divide?
29. The starting location for chromosomal replication in bacteria is known as
what?
30. What serves as the template for DNA replication in bacteria?
31. Identify the product of binary fission.
Homework
32. Where are genes found?
33. What does DNA stand for?
34. In DNA replication, guanine pairs with ____________________.
35. What basic “building block” molecule is DNA composed of?
36. Describe the structure of a bacterial DNA.
37. In which direction does DNA unwind in bacteria?
38. Describe a replication bubble.
39. Give a brief explanation of what binary fission is.
40. When does binary fission occur?
Class Work
41. Identify three sources of genetic variation in bacteria.
42. Identify the two strains of bacteria used in Griffith’s experiment.
43. Describe each of the four trials that Griffith performed in his experiment and
the results of each.
44. Define conjugation.
45. In which direction does conjugation occur?
46. Describe what plasmids are.
47. What is the “F factor”?
48. What is the significance of the “R factor”?
Homework
49. Define transformation as it pertains to bacteria cells.
50. Identify the scientist that was the first to research transformation.
51. What conclusion was reached through Griffith’s experiment?
52. From the conclusion of Griffith’s experiment, what greater generalization can
be made of bacteria’s’ ability to add variation to its chromosome?
53. Identify the organelle that is used in conjugation.
54. What distinguishes a “male” bacterium from a “female” bacterium and allows
for the growth of a sex pillus?
55. How does a bacteria receive an R plasmid?
Class Work
56. Define virus.
57. List three reasons that viruses are considered “not living”.
58. Which part of a virus helps it to attach to bacteria?
59. Each virus has a limited number of cells that it can affect, this is known as its
______________________.
60. Briefly describe what happens during the lytic cycle of a bacteriophage?
61. Identify and describe one defense that bacteria have against phages?
Homework
62. Explain how a virus invades bacteria.
63. Define bactriophage.
64. Which part of a virus contains the DNA?
65. What does it mean when we describe viruses as obligate intracellular
parasites?
66. When a bacteriophage invades bacteria, what part of the bacteriophage
enters the bacteria cell?
67. What happens to the host cell at the end of the lytic cycle?
Class Work
68. How does the lysogenic cycle differ from the lytic cycle?
69. Describe what occurs when a temperate phage switches from a lysogenic to a
lytic cycle.
70. Define transduction.
Homework
71. How is virus DNA spread throughout a bacteria colony when it is in a
lysogenic cycle?
72. What are temperate phages?
73. How is transduction beneficial to a bacteria colony?
Class Work
74. What molecule undergoes transcription?
75. What is the product of transcription?
76. What is the product of translation?
Homework
77. How many amino acids are there?
78. How many codons are there?
79. List the nucleotide bases of RNA.
80. What type of RNA is translated into protein?
Class Work
81. Bacteria cells are able to regulate what cellular process to adapt to changes in
their environment?
82. Describe the structure of an operon.
83. How can an operon be switched off?
84. Identify the two molecules used in the allosteric regulation of the repressor.
85. Define inducible operon.
86. Describe the role of the lac operon.
87. Define repressible operon.
88. Describe the role of the trp operon.
89. Define symbiosis.
Homework
90. List two examples of ways that bacteria can regulate their gene expression?
91. What is the role of the operator?
92. What is the role of the promoter?
93. Name the molecule that works with the repressor to help switch the operon
off.
94. Name the molecule that works with the repressor to help switch the operon
on.
95. Identify one advantage to bacteria for being able to turn genes on and off.
96. The trp operon is present on the E. coli in the human digestive system.
Describe an example of when the trp operon would be shut off.
97. List and define the 3 types of symbiosis.
98. Explain how symbiosis is helpful to prokaryotes.
99. Why are good symbiotic relationships favorable in natural selection?
Free Response
1. Protobionts were precursors to life and prokaryotes were the first living
organisms.
a. Identify and describe the function of three important organelles in
bacteria.
b. Explain the structural difference between a gram positive and a gramnegative bacteria cell.
c. Through the process of gram staining, describe the expected results
for a gram-positive bacteria cell and a gram-negative bacteria cell.
d. Explain how the discovery of gram staining impacted the medicinal
world?
2. One of the key characteristics of living things is that they are able to
reproduce on their own.
a. Describe the structure of bacteria’s DNA.
b. Identify and describe the process by which bacteria cells reproduce.
c. If a given bacteria cell is able to reproduce every 20 minutes, and you
inoculate a culture of 50 bacteria cells, how many bacteria cells would
you have after 4 hours?
3. Viruses are small, non-living particles that can infect other organisms.
a. Identify the name for viruses that can infect bacteria.
b. Provide three pieces of evidence to support the conclusion that
viruses are “non-living”.
c. Describe how viruses are able to spread through a colony of bacteria
without the production of phages.
d. Describe the lytic cycle of a virus.
4. Genetic variation is necessary for survival and evolution.
a. Explain the results of Griffith’s experiment and identify what
mechanism of genetic variation his experiment was an example of.
b. The transfer of bacterial DNA from one bacteria cell to another by a
virus is an example of what mechanism of genetic variation in
bacteria? Explain how this is able to occur.
c. A scientist is presented with colonies of two different strains of
bacteria; strain A and strain B. He takes each strain separately, mixes
it with soft agar, and spreads it over a plate so that an even lawn of
bacteria grows in each plate. Next, the scientist adds a small paper
disc soaked in penicillin to each plate. When he comes back 24 hours
later, he notices that there is a zone of inhibition around the paper
disc in plate A, but not in plate B. Assuming no human error, provide
an explanation for these results.
d. The results obtained in plate B of the scientist’s experiment are an
example of what mechanism of genetic variation in bacteria?
5. Many sexually transmitted diseases such as HIV, herpes, and syphilis can go
undetected without medical testing. (*The specifics of animal virus
transmission differ from that of bacteriophages, but the generalities are
similar.)
a. Explain what characteristic these viruses must have.
b. What is a possible consequence that a person infected with HIV may
not develop any symptoms for years?
c. Based on your knowledge of viruses, when a person goes from having
an HIV infection to having AIDS, what is occurring?
6. Gene expression is the process by which information from genes is used to
make functional protein products.
a. List the steps of gene expression in bacteria.
b. Describe briefly how gene expression can be regulated in bacteria.
c. Explain one example of the control of gene expression in bacteria.
d. Why is the ability to control gene expression beneficial to bacteria?
Prokaryotes & Viruses Answers
1. Prokaryotes
2. Bacteria
3. Bacteria are found in our
digestive systems and are used
to make antibiotics.
4. The entire organism is made of
only one cell.
5. Colonies
6. Archaea
7. Organelles
8. The cell wall is composed of
peptidoglycan and most
prokaryotes also have a
capsule made of a sticky
polysaccharide or protein
covering their cell wall.
9. Pili are made from protein and
grow from the cell membrane
10. There are short attachment pili
known as fimbriae and there
are long sex pili.
11. Flagella
12. Protobiont
13. Acidic places, cold places, hot
places, salty places
14. Microscopic in size
15. Antibiotics, breast milk, cheese,
yogurt
16. Prokaryotes are unicellular
organisms that occur in many
different shapes including:
cocci, bacilli, rod, and budding
shapes
17. They are able to survive in
extreme environments where
no other living organisms are
able to survive.
18. Outside the cell membrane
19. Keeps the cell’s shape, provides
protection, keeps the cell from
bursting in hypotonic
environments
20. Fimbriae are used to help the
bacteria attach and adhere to a
surface
21. Taxis is the ability to move in
response to a stimuli
22. The basal apparatus connects
the flagella to the plasma
membrane and acts as a
spinning motor. The filament
is the long part of the flagella
that oscillates through the
environment. The hook
connects the basal apparatus to
the filament and causes the
filament to oscillate.
23. DNA
24. Locus
25. DNA is a double helix molecule
composed of a sugarphosphate backbone and
nucleotide bases
26. Adenine
27. A series of 3 nucleotide bases
that code for a specific amino
acid
28. Binary Fission
29. Origin of Replication
30. Both strands of the bacterial
DNA that are inside the
replication bubble
31. Two singular bacterial
chromosomes containing one
parent strand and one
daughter strand
32. On chromosomes at specific
loci
33. Deoxyribonucleic acid
34. Cytosine
35. Nucleotides
36. Bacterial DNA is found in one
singular circle chromosome
within each bacteria cell
37. It unwinds in both directions
within the replication bubble.
38. A replication bubble is formed
when the DNA unwinds in both
directions at the origin of
replication, creating two
replication forks. The
replication bubble consists of
the two template strands of
DNA.
39. Binary fission is the process
through which bacteria cells
are able to replicate. In binary
fission, the chromosome is
duplicated and the bacteria cell
splits into two separate cells,
each containing one
chromosome.
40. Binary fission occurs after DNA
replication
41. Transformation, conjugation,
transduction
42. A pathogenic smooth strain “s”
and a harmless rough strain “r”
43. First Trial: Rough strain
bacteria were injected into
mice and the mice lived.
Second Trial: Smooth strain
bacteria were injected into the
mice and the mice died. Third
Trial- Heat-killed smooth strain
bacteria were injected into the
mice and the mice lived.
Fourth trial- Rough strain
bacteria and heat-killed
smooth bacteria were injected
into the mice and the mice
died.
44. Conjugation is the direct
transfer of genetic material
between bacteria cells that are
temporarily joined through a
sex pilus.
45. Conjugation occurs from the
“male” bacteria (the one
containing the F factor, F+) to
the “female” bacteria (F-)
46. Plasmids are small, circular,
self-replicating DNA found in
addition to but separate from
the bacterial chromosome that
are able to transfer genes from
one bacteria cell to another.
47. The “F factor” is the bacterial
plasmid that allows for fertility
by containing the genes for sex
pilus formation.
48. The “R factor” is a plasmid that
allows for antibiotic resistance.
When a bacterium has the “R
factor” for a particular
antibiotic and is exposed to
that antibiotic, the bacterium is
able to survive.
49. Transformation is the
alteration of bacterial cell’s
genes by the uptake of DNA
from the surrounding
environment. The bacterium
takes in DNA from its
environment and incorporates
it into its own chromosome
causing a change in genotype
and phenotype.
50. Frederick Griffith
51. The harmless rough strain
bacteria took in the heat-killed
smooth strain bacteria’s DNA,
which caused a change in the
genotype and phenotype of the
smooth strain bacteria making
it pathogenic and causing the
mice to die.
52. Bacteria are able to add
variation to their DNA by
taking in DNA from the
surrounding environment.
53. Sex pillus
54. The “male” bacterium is F+
meaning that it has the “F
factor” or F plasmid and is able
to form a sex pilus. The
“female” bacterium is F- and
therefore cannot form a sex
pilus.
55. Through conjugation
56. Small, non-living particles that
infect living organisms
57. Virus are considered non-living
because they are not made of
cells, cannot reproduce on their
own, and cannot metabolize
food or process energy
58. Tail fibers
59. Host range
60. The bacteriophage injects its
DNA into the bacteria. The
bacteria’s DNA is destroyed.
The bacteriophage’s DNA
instructs the bacteria cell to
make new phages. The
bacteria cell is killed through
lysis and the new phages are
released.
61. Restriction enzymes recognize
and cut up phage DNA.
62. The bacteriophage attaches to
the bacteria with its tall fibers.
The bacteriophage injects its
DNA into the bacteria. The
bacteria’s DNA is destroyed.
The bacteriophage’s DNA
instructs the bacteria cell to
make new phages.
63. A bacteriophage is a virus that
is able to infect bacteria.
64. The head
65. They are only able to
reproduce inside a host cell
66. The DNA
67. The host cell dies.
68. In the lysogenic cycle, the
virus’s DNA is incorporated
into the bacteria’s DNA. Also,
new phages are not formed and
the host cell is not killed.
69. When a temperate phage
switches from a lysogenic to a
lytic cycle, the phage DNA is
separated from the bacteria’s
DNA. The bacteria’s DNA is
destroyed, the phage DNA
instructs the cell to make more
phages.
70. Transduction is the process by
which bacterial DNA is
transferred from one
bacterium to another by a
virus.
71. Since the virus’s DNA is
incorporated into the bacteria’s
DNA, it is replicated along with
the bacteria’s DNA and
incorporated into more cells
through binary fission.
72. Temperate phages are viruses
that are able to use both the
lytic and lysogenic cycles.
73. Transduction is beneficial to a
bacteria colony because it
provides variation in bacterial
DNA by transferring DNA from
one bacteria cell to another.
74. DNA
75. RNA
76. Protein
77. 20
78. 64
79. adenine, guanine, cytosine,
uracil
80. mRNA
81. Gene expression
82. An operon consists of genes, an
operator, and a promoter.
83. An operon can be switched off
by the binding or release of a
repressor protein.
84. Co-repressors and inducers
85. An inducible operon is an
operon that is usually off.
86. The lac operon is responsible
for controlling the genes that
code for the break down of
lactose into glucose.
87. A repressible operon is an
operon that is usually on.
88. The trp operon controls the
genes responsible for the
production of tryptophan.
89. Symbiosis is the interaction of
organisms from two different
species through direct contact,
which provides benefit to one
or both organisms.
90. Through the lac operon and trp
operon
91. The operator is an “on-off”
switch for gene expression.
92. The promoter is a sequence of
RNA that attracts RNA
polymerase for the initiation of
transcription.
93. Co-repressor
94. Inducer
95. Conservation of Energy
96. After a person has eaten a meal
consisting of turkey.
97. Mutualism is symbiosis when
both organisms benefit.
Commensalism is symbiosis
when one-organism benefits
and the other organism is
neither helped nor harmed.
Parasitism is when one
organism benefits at the
expense of the other.
98. Symbiosis is helpful to
prokaryotes because their DNA
is small so they do not always
contain the DNA necessary to
code for all the materials they
need to survive, however they
can get these materials through
symbiosis.
99. Good symbiotic relationships
are favorable in natural
selection because they help the
organisms to survive and they
increase the complexity of
biological systems.
Free Response Answers
1.
a. The cell wall provides protection, shape, and keeps the cell from
bursting in a hypotonic environment. The flagellum allows the cell to
have mobility. The short pili allow the cell to attach to surfaces and
long sex pili allow for conjugation.
b. Gram-positive bacteria have thicker peptidoglycan cell walls. Gramnegative bacteria have thinner peptidoglycan cell walls and an outermembrane made of lipopolysccaharides.
c. When gram staining is performed, gram-positive bacteria will appear
purple and gram-negative bacteria will appear pink.
d. Since gram staining can be used to identify whether a bacteria is
gram-positive or gram-negative, antibiotics specific to gram-positive
or gram-negative bacteria can be prescribed instead of using broadspectrum antibiotics that attack both types of bacteria.
2.
3.
a. Each bacteria cell contains one single, circular double-stranded DNA
loop.
b. Bacteria cells reproduce through binary fission. Each bacteria cell
undergoes DNA replication to produce two loops of DNA, then the cell
splits into two with each resulting bacterial cell containing one of the
two loops of DNA.
c. 212 X 50 = 204,800 bacteria cells
a. Bacteriophages
b. Viruses are considered “non-living” because they cannot reproduce on
their own, they do not metabolize, and they are not made of cells.
c. Viruses are able to spread through a colony of bacteria if they enter
their lysogenic cycle. In the lysogenic cycle the virus’s DNA is
incorporated into the bacteria’s DNA where it is then replicated along
with the bacteria’s DNA and incorporated into new bacteria cells
through binary fission.
d. In the lytic cycle of a virus, the virus attaches to the bacteria and
inserts its own DNA. The bacteria’s DNA is destroyed and the viral
DNA directs the cells to make new phages. The cell then dies when it
is lysed to release the new phages.
4.
5.
a. Griffith’s experiment was an example of transformation. In his
experiment he used a pathogen smooth strain of a bacteria and a
harmless rough strain of the bacteria. When he injected only the
rough strain into mice, they lived. When he injected only the smooth
strain into mice, they died. When he injected heat-killed smooth
strain bacteria in mice, they lived. When he injected both the rough
strain of bacteria and the heat-killed smooth strain, the mice died.
These results indicated that the rough strain of bacteria was able to
uptake the heat-killed smooth strain bacteria DNA, which caused the
strain to become pathogenic and result in death of the mice.
b. This is an example of transduction. Transduction occurs when a piece
of bacterial DNA is incorporated with the viral DNA as the virus
changes from the lysogenic to lytic cycle. When the new phages
produced in the lytic cycle infect new host bacteria, the bacterial DNA
from the previous host is incorporated into the DNA of the new host
bacteria cell.
c. The zone of inhibition around the paper disc in plate A is caused by
the death of the strain A bacteria from penicillin. The lack of a zone of
inhibition in plate B, indicated that the strain B bacteria had antibiotic
resistance for penicillin.
d. Conjugation
a. These viruses are able to enter a lysogenic cycle.
b. The person can be unaware that they have HIV and therefore transmit
the virus to others.
c. When a person goes from being infected with HIV to having AIDS, the
HIV virus has changed from a lysogenic to a lytic cycle and is killing
the host cells in the immune system.
6.
a. DNA replication to Transcription to Translation
b. Gene expression can be regulated through the use of operons, which
can turn the expression of genes on and off.
c. Either an explanation of how the trp or lac operon work would be
acceptable.
i. trp operon- is a repressible operon meaning it is usually on.
The genes controlled by the trp operon are responsible for
producing tryptophan, however if tryptophan is present in the
environment of the bacteria the operon can be shut off.
ii. lac operon- is an inducible operon meaning it is usually off.
The genes controlled by this operon produce the enzyme that
breaks down lactose into glucose. This operon is turned on
when lactose is present in the environment of the bacteria.
d. The ability to control gene expression allows the bacteria cell to save
energy.