Exam 8: Viruses and Their Replication

Although bacteria lack an immune system, they do possess several weapons against viral attack. Explain the mechanisms utilized by bacteria to prevent viral infection.

T4 and other bacteriophages commonly use a method of DNA replication and packaging called ʺheadful packaging.ʺ Explain how viral genomes are replicated and packaged in this process and hypothesize how headful packaging might affect evolution of BOTH the bacteriophages and their prokaryotic hosts.

all viral particles

Viral size is generally measured in

You are attempting to mutate lambda to affect whether lysis or lysogeny occurs after infection. Which mutation would INCREASE the chances of LYSOGENY over lysis?

Why have the majority of viruses evolved to bind to a host surface receptor that serves an essential function in the host cell?

You isolate a bacteriophage that can replicate in E. coli. Through chemical analyses you determine that the only nucleic acid present is RNA. You isolate the RNA and put it in a test tube with all of the enzymes, amino acids, and RNAs necessary for translation. The RNA is translated directly, without being copied into a complementary strand first, and new infectious virions are made and released. What does this tell you about the bacteriophage?

Retroviruses are medically important viruses because

Enveloped viral membranes are generally ________ with associated virus-specific ________.

Budding of virions from an infected host results in enveloped virus.

The term ʺphageʺ is generally reserved for the viruses that infect

Prokaryotic restriction endonucleases are effective at destroying a virus whose genome consists of

What are the possible consequences of viral infection of an animal cell?

The genome of retroviruses contains genes to make all of the following EXCEPT

Viruses variously depend on their host cell for parts of the viral replication and maturation process. Many viruses do however encode for some enzymes that facilitate certain steps or virus-specific processes for viral replication and maturation. Which cellular processes and enzymes do all viruses lack and must therefore ALWAYS be supplied by the host cell?

The genome of a retrovirus consists of dsRNA.

Which of the following enzymes would you expect to find in the virion of a retrovirus, but NOT in a bacteriophage?

The genome of a temperate phage can replicate along with the host genome during lysogeny.

As a consequence of infection by a temperate bacteriophage such as lambda, the host cell

Influenza is an acute human viral disease that causes brief cellular damage followed by healing and complete clearing of the virus from the body. Hepatitis C is a chronic viral disease that causes slow destruction of liver tissue and persistent virions that are not completely cleared. Which of these diseases is more likely to be caused by lytic virus and which is caused by a non-lytic virus?