State two structural features common to all viruses.

State one cellular structure absent from all viruses.

Define a capsid.

Outline why viruses cannot synthesize proteins independently.

Distinguish between an enveloped virus and a non-enveloped virus.

Give one example of each type from the syllabus.

State two ways in which viral genomes vary.

Identify the enzyme characteristic of retroviruses such as HIV.

State the host organism used as the example for bacteriophage lambda replication.

Outline how lambda DNA enters the host cell during infection.

Identify the virus type most likely represented by X, a head-and-tail particle infecting bacteria.

Identify the virus type most likely represented by Y, an enveloped particle with crown-like spikes and an RNA genome.

Identify the virus type most likely represented by Z, an enveloped RNA virus carrying reverse transcriptase.

State one structural feature common to X, Y and Z.

State why viruses are described as non-cellular.

Outline two ways in which this non-cellular structure affects viral reproduction.

State what a decrease in optical density indicates about the bacterial culture.

Identify the stage of the lytic cycle most directly responsible for the decrease.

Explain why phage number can increase while bacterial optical density decreases.

Describe the range of particle diameters shown.

Compare viral particle sizes with typical bacterial cell sizes.

Suggest why viral particles do not increase in size after assembly.

Outline the role of specific receptors during attachment.

State what is released during lysis.

State one host resource used during genome replication or translation.

State what a prophage is.

Compare the outcomes of the lytic and lysogenic cycles in bacteriophage lambda.

State one feature shared by viruses and living organisms that suggests an evolutionary link.

Explain why this feature is important for viral replication.

State two reasons why HIV evolves rapidly.

Explain one consequence of rapid HIV evolution for treatment.

Define a segmented genome.

Explain how segmented genomes contribute to rapid evolution of influenza viruses.

State two selection pressures acting on viruses inside a host population.

Explain how one selection pressure can change the frequency of viral variants.

Identify the time period during which viral genome copies increase most rapidly.

Describe the relationship between genome copies and infectious particles.

Suggest why infectious particles appear later than genome copies.

Identify the virus most likely to be a retrovirus.

Identify the virus most likely to be a bacteriophage similar to lambda.

Compare the diversity of genome type shown by the viruses.

Suggest one reason why envelope presence is not a reliable feature for classifying all viruses into one evolutionary group.

Identify the condition under which lysogeny is most frequent.

Describe the pattern for lytic infection as host cell density increases.

Suggest an advantage of lysogeny when host cells are scarce.

Identify which virus is most likely enveloped.

Explain the effect of detergent on the enveloped virus.

Suggest why the other virus remains infectious after detergent treatment.

Outline the progressive origin hypothesis for viruses.

Suggest why the common features of viruses may be examples of convergent evolution.

State the viral life cycle that may allow lambda DNA to persist without immediate host lysis.

Suggest two advantages of this life cycle for the virus under these conditions.

State what can happen later if the integrated viral DNA becomes active.

State one reason why a single origin of all viruses is difficult to support.

Evaluate the claim that evolution always leads to increased complexity, using viruses as an example.

Describe the change in frequency of the resistance mutation after treatment begins.

Explain how natural selection could cause this change.

Suggest why adding a second drug with a different target may reduce treatment failure.

Describe the relationship between amino acid differences and antibody binding.

Suggest why this relationship may reduce the effectiveness of an influenza vaccine.

State the main pattern in the number of genes shared by all virus groups.

Compare the pattern of gene sharing among viruses with the pattern among cellular organisms.

Evaluate how these data support the hypothesis of several origins of viruses.

Outline the first two stages in infection of Escherichia coli by bacteriophage lambda.

Compare and contrast the lytic and lysogenic cycles of bacteriophage lambda.

State two features that viruses lack compared with living cells.

Explain how viruses can reproduce despite having few genes and lacking cell structure.

Identify one structural feature of each of the following: bacteriophage lambda, a coronavirus and HIV.

Compare and contrast the diversity of structure and genome organization in these three virus examples.

State the result for cells infected with strain P only.

Describe the evidence that reassortment occurred in co-infected cells.

Explain how reassortment can increase the rate of influenza evolution.

Outline two structural features common to all viruses.

Discuss evidence that viruses may have had several origins from other organisms rather than one single origin.

State three factors that can cause rapid evolution in some viruses.

Explain how rapid evolution occurs in influenza viruses and why this affects prevention of influenza.

Outline the role of reverse transcriptase in HIV replication.

Evaluate why rapid evolution makes HIV difficult to treat.

Outline two ways in which viral genetic variation is generated.

Evaluate the consequences of rapid viral evolution for vaccination and antiviral drug use, using influenza and HIV as examples.

Define obligate parasitism in the context of viruses.

Discuss how viruses illustrate both simplification and convergent evolution in the history of life.