lab 2 ch 17

Diagram and explain the life cycles of lytic and lysogenic viruses.

1 Viruses that have a lytic life cycle will cause the host cell to burst or lyse, releasing the viral particles. Each particle in turn can then infect a healthy host cell. Virulent viruses undergo only the lytic cycle. 2 In contrast to lytic viruses, lysogenic viruses allow for the integration and replication of the viral genome in the host cell without destroying the host. Thus, the virus genome is passed along as the host cell reproduces. Prophages are the result of integration of the viral genome into the bacterial genome. Temperate viruses undergo both lytic and lysogenic stages.

Explain the action of a typical bacteriophage attack.

Classically, a typical bacteriophage life cycle consists of five distinct phases. 1 Adsorption or attachment. The virus recognizes the protein signature of a host cell and attaches to the host cell. 2 Entry or penetration. During this stage, the viral genome is inserted into the host cell. 3 Integration. In this step, the viral genetic material combines with genetic material of the host cell, forming a prophage. 4 Synthesis and assembly. This phase involves replication of the viral genome and synthesis of the viral capsid. During assembly, the viral particles mature. 5 Release. This final stage usually results in lysis of the host cell. The number of viroids released during this stage is variable.

Describe how a disease can be transmitted in a population.

Each year, viral diseases such as the cold virus and the flu virus cause disease in humans. These are communicable diseases spread from one person to another by contact through coughing and sneezing. Other viral diseases, such as hepatitis, AIDS, and genital herpes, are transmitted by sharing body fluids.

Discuss five significant families of viruses and the diseases they cause.

Five significant families of viruses include: Herpesvirus—Enveloped—herpes simplex type I—cold sores; herpes simplex type II—genital herpes, mononucleosis, Epstein Barr, shingles, Burkitt's lymphoma. Poxvirus—Enveloped—smallpox, monkeypox. Retrovirus—Enveloped—human immunodeficiency virus (HIV), Simian immunodeficiency virus (SIV), feline immunodeficiency virus, mouse mammary tumor virus, chimpanzee foamy virus. Filovirus—Enveloped—Ebola, Marburg, Reston Rhabdovirus—Enveloped—rabies, lettuce necrotic yellow virus

Define the term virus, and identify what organisms viruses can infect.

In Latin, the term virus means "poison". Viruses are simple, they are small, infectious particles. Many of the diseases that plague plants, animals, and humans are known to be caused by viruses. Fungi and bacteria fall victim to viruses as well.

Describe the structure of prions, and name several diseases caused by prions.

Prions are proteinaceous infectious particles. Prion diseases affect the nervous system, causing neurological damage and death. Examples of prion diseases include scrapie in sheep and goats, Creutzfeldt-Jakob disease (CJD), kuru in humans, and bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, in cattle.

Compare and contrast enveloped and naked viruses.

Some viruses, called envelope viruses, are encased in an envelope derived from the host cell. Among envelope viruses are those responsible for HIV, herpes, smallpox, influenza and rabies. Those that do not contain an envelope are called naked viruses. Naked viruses are responsible for warts, polio, and Hepatitis A

Describe the different shapes of viruses.

The shape of viruses can range from spherical to brick-shaped to helical, and from icosahedral to polyhedral.

Define viroids, and identify several diseases caused by viroids.

Viroids cause diseases in plants. Theodor Diener discovered and named these plant pathogens in 1971. Structurally, viroids consists of a circular strand of RNA only a few hundred bases in length. The viroids can be transmitted by pollen grains or seeds, by sucking insects such as aphids, and even from pruning. Among viroid diseases are potato spindle tuber disease and coconut cadang-cadang.

What are the anatomical features of a typical virus?

Viruses are small, infectious particles consisting of a protein coat surrounding a core of DNA or RNA. One of the smallest viruses is only 20 nm in diameter, and the largest is barely visible under a light microscope. Millions of virus particles known as virions can fit in a typical human cell. All viruses have an outer protein coat known as a capsid. Capsids are constructed from protein subunits termed capsomeres.