While studying with a fellow classmate, you ask them for help determining the differences between viruses and cells. Your classmate tells you that viruses are different from cells because viruses cannot replicate autonomously. They also indicate that all viruses contain both DNA and RNA that is double stranded, have many enzymes, and are much smaller than cells. Lastly, they tell you that all viruses contain nucleic acid surrounded by a protein coat. Provide three separate reasons why your classmate is incorrect in their comparison of viruses and cells. For the toolbar, press ALT+F10 (PC) or ALT-FN-F10 (Mac). R T U f Paranranh Y Arial 100t

The genome of a virus consists of (a) DNA (b) RNA (c) prions (d) DNA and RNA (e) DNA or RNA

Which statement is true? A virion contains DNA and RNA Viruses are acellular Viruses replicate outside of the cell Most viruses are easily visualized with a light microscope.

In _______, viral DNA becomes integrated into a bacterial chromosome and is passed to descendant cells. a. binary fission c. the lysogenic pathway b. the lytic pathway d. conjugation

When a virus enters the lysogenic stage: a. the viral DNA is replicated outside the host cell. b. it enters the host cell and kills it immediately. c. it enters the host cell, picks up host DNA, and leaves the cellunharmed. d. it sits on the host cell plasma membrane with which it coversitself and then leaves the cell. e. the viral DNA integrates into the host genome.

The viral ________ plays a role in attaching a virion to the host cell. a. core b. capsid C. envelope d. both b and c

An apple grower notices that several of his apple trees with fungi growing on their trunks have developed necrotic ring spots, while other trees in the orchard that lack fungi appear healthy. What is the most likely conclusion the farmer can make about the virus infecting his apple trees? The apple trees were infected by horizontal transmission The fungi carry disease The fungi attract disease-carrying insects The apple trees were infected by vertical transmission.

In this section, you were introduced to different types of viruses and viral diseases. Briefly discuss the most interesting or surprising thing you learned about viruses.

Figure 21.10 Which of the following statements is false? In the lytic cycle, new phages are produced and released into the environment. In the lysogenic cycle, phage DNA is incorporated into the host genome. An environmental stressor can cause the phage to initiate the lysogenic cycle. Cell lysis only occurs in the lytic cycle.

There have been recurring cases of mad-cow disease in the United Kingdom since the mid-1990s. Mad-cow disease is caused by a prion, an infectious particle that consists only of protein. In 1986, the media began reporting that cows all over England were dying from a mysterious disease. Initially, there was little interest in determining whether humans could be affected. For 10 years, the British government maintained that this unusual disease could not be transmitted to humans. However, in March 1996, the government did an about-face and announced that bovine spongiform encephalopathy (BSE), commonly known as mad-cow disease, can be transmitted to humans, where it is known as variant Creutzfeldt-Jakob disease (vCJD). As in cows, this disease eats away at the nervous system, destroying the brain and essentially turning it into a spongelike structure filled with holes. Victims experience dementia; confusion; loss of speech, sight, and hearing; convulsions; coma; and finally death. Prion diseases are always fatal, and there is no treatment. Precautionary measures taken in Britain to prevent this disease in humans may have begun too late. Many of the victims contracted it over a decade earlier, when the BSE epidemic began, and the incubation period is long (vCJD has an incubation period of 10 to 40 years). A recent study concluded that 1 in 2,000 people in Great Britain carry the abnormally folded protein that causes vCJD. In spite of these numbers, the death rate from vCJD remains low. It is not clear whether this means that the incubation period for the disease is much longer than previously thought, or whether they may never develop the disease. What measures have been taken to stop BSE?