BIO182 Chapter 19 MasteringBiology Homework
Which statements about viruses are true? Select the four statements that are true.
-Enveloped viruses bud from the host cell. -A retrovirus contains RNA. -HIV contains reverse transcriptase. -The capsid enters the host cell if the virus is enveloped.
Which of these binds to receptor molecules on the host cell membrane?
A
Referring to the phylogenetic tree in Figure 1, which variant is more closely related to A/Taiwan1018/2011 in group 9 (brown): A/Taiwan/552/2011 or A/Taiwan/8542/2009? (For help reading the phylogenetic tree, see the hint.)
A/Taiwan/552/2011; variants 1018/2011 and 552/2011 share a more recent common ancestor than is shared with variant 8542/2009.
A new disease emerges and exists only as a free-floating virus. Which of the following will make antibodies against this?
B cells
Which of these is reverse transcriptase?
C
Which of these is the viral genome?
E
Which group of variants was the earliest to cause H1N1 flu in over 100 patients in Taiwan?
Group 7 (black line)
The best flu vaccine would work to prevent people from which of the following?
Influenza A, B, and C
What is the function of reverse transcriptase?
It catalyzes the formation of DNA from an RNA template.
Classify each phrase as applying to the lytic cycle, the lysogenic cycle, or both types of reproductive cycles of phages.
Lytic Cycle- the cell is lysed (broken open), new phages are assembled from viral DNA ad proteins, the host is destroyed Lysogenic Cycle- the cell reproduces normally, the viral DNA integrates into the chromosome of the host cell Both Cycles- viral genes are replicated
Once a group of variants had a peak number of infections, did members of that same group cause another wave of infection?
No, each group of variants caused only one wave of infection.
Do all of the groups have the same number of branches or branch tips? What does this result indicate?
No; some groups experienced a higher mutation rate than others.
How do prions, which are misfolded proteins, infect organisms?
Prions enter brain cells and cause normal forms of the protein to refold into the prion form.
What kind of cell can recognize infected cells and kill them directly?
T cells
Why is combination drug therapy for HIV/AIDS less likely to lead to resistance than single drug therapy?
The likelihood of one virus spontaneously mutating to be resistant to several different drugs at the same time is extremely small.
A plant that has been raised in a sterile environment shows symptoms of a viral infection. How would you explain this?
The viral infection was acquired by vertical transmission.
Which of the following statements about viruses is FALSE?
The widespread use of antibiotics has led to resistant strains of viruses.
Groups 9, 10, and 11 all had H1N1 variants that caused a large number of infections at the same time in Taiwan. Does this mean that the scientists' hypothesis, that new variants cause new waves of infection, was incorrect? Explain your answer.
Their hypothesis was still supported; these three groups arose along different lineages but emerged to cause illness during the same wave.
Sort the items according to whether they may be found only in free virus particles, only in uninfected host cells, or in both viruses and host cells.
Viruses only- Capsid, Capsomere (core protein), Envelope with glycoproteins Host cell only- Ribosome Both- Protein, RNA, DNA
One variant in the green groups (Groups 1, 3, and 6) was used to make a vaccine that was distributed very early in the pandemic. Based on the graphed data, does it look like the vaccine was effective? Why or why not?
Yes, it was effective; the green line never reaches 100 on the y-axis.
Which of the following can be found in bacteria, but not viruses?
a cell membrane
The H1N1 2009 outbreak is considered to have been which of the following?
a pandemic
Suppose you were in charge of sending an unmanned space probe to a new planet in search of life. The probe would be able to collect and test samples and make observations, but the planet is too far away for the probe to be able to bring samples back to Earth. The probe is small and would only be able to run a few tests, so you want to pick a test for evidence of life that is broad enough to incorporate all forms of life as we know it. Which one of the following tests would be the best to use in this situation?
a test for the presence of cells that contain DNA
Homeostasis is a living organism's
ability to maintain constant internal conditions even when environmental conditions change.
The nucleic acid of a virus particle is enclosed in a protein coat. What is it called?
capsid
Which of the following is NOT a characteristic of living things?
creating energy
The pointer is indicating the virus's _____.
genome
What is the source of a viral envelope?
host cell membrane
Cycle A is the _____ cycle and cycle B is the _____ cycle.
lytic ... lysogenic
Viruses are
not alive because they are not made of cells and require a host cell for reproduction.
A disease that spreads rapidly around the world is called a(n) ___________.
pandemic
What do we call a virus that attacks a bacterium?
phage
You are an immunologist working on a new flu vaccine that attacks molecules with the same basic make-up as hemagglutinin. What is your area of expertise?
proteins
Double-stranded viral DNA is incorporated into a host cell as a _____.
provirus
Click on the diagram to start the animation. What enzyme is responsible for the process seen here?
reverse transcriptase
HIV uses which of the following processes to synthesize a DNA strand using its RNA genome as a template?
reverse transcription
The lytic cycle of bacteriophage infection ends with the _____.
rupture of the bacterium
The genetic material of HIV consists of _____.
single-stranded RNA
As a result of the lytic cycle, _____.
the host cell's DNA is destroyed
Viral DNA makes mRNA by the process of _____.
transcription
What is the most effective way to stop viral infections?
vaccines
In the lysogenic cycle _____.
viral DNA is replicated along with host DNA
The pointer is indicating the _____.
viral protein coat
