Unit 4 (Week 15 Genetics of Viruses and Bacteria) Flashcards
In bacterial meningitis, what do the meninges do?
They cause inflammation of the protective membranes that cover the brain and spinal cord.
Bacterial meningitis is up to six times more common among people living in close quarters, such as college dormitories.
What is a virus or microorganism that causes disease symptoms in its host?
A pathogen.
How do bacteria, even though they reproduce asexually, have their genetic variety enhanced?
A phenomenon called gene transfer, in which genes are passed from one bacterial cell to another.
Like sexual reproduction in eukaryotes, gene transfer enhances the genetic diversity observed among bacterial species.
[19.1 General Properties of Viruses]
What are nonliving particles with nucleic acid genomes?
Viruses
How does a virus or its genetic material replicate?
It must be taken up by a living cell.
What was the first discovered virus and subsequent viruses before 1900?
Tobacco mosaic virus (TMV), cattle disease (foot-and-mouth disease), and the first human virus, yellow fever.
TMV can spread the disease but spraying sap from one plant to another. Filtering the sap, the sap still caused the disease ruling out bacteria. Also, toxic chemical was thought to be the issue, but after several generations of the plants, the disease still remained which wouldn’t if it was a toxin since the toxin would be diluted.
What is a small infectious particle that consists of a nucleic acid enclosed in a protein coat?
A virus.
Researchers have identified and studied over 4,000 different types of viruses.
What similarities do all viruses share?
Small size and reliance on a living cell for replication.
What vary greatly in the characteristics of a virus?
The host range, structure, and genome composition.
{Information: Hosts and Characteristics of Selected Viruses]
Order = Virus or group of viruses, Host, Effect on Host, Nucleic Acid, Genome Size, and Number of Genes. (also saved on drive)
Virus or group of viruses Host Effect on host Nucleic acid* Genome size (kb)† Number of genes†
Phage λ
E. coli
Can exist harmlessly in the host cell or cause lysis
dsDNA
48.5
36
Phage T4
E. coli
Causes lysis
dsDNA
169
288
Tobacco mosaic virus (TMV)
Many plants
Causes mottling and necrosis of leaves and other plant parts
ssRNA
6.4
6
Baculoviruses
Insects
Most baculoviruses are species specific; they usually kill the insect
dsDNA
133.9
154
Influenza virus
Mammals
Causes classical “flu,” with fever, cough, sore throat, and headache
ssRNA
13.5
11
More Viruses
Epstein-Barr virus
Humans
Causes mononucleosis, with fever, sore throat, and fatigue
dsDNA
172
80
Adenovirus
Humans
Causes respiratory symptoms and diarrhea
dsDNA
34
35
Herpes simplex type II
Humans
Causes blistering sores around the genital region
dsDNA
158.4
77
HIV (type I)
Humans
Causes AIDS, an immunodeficiency syndrome eventually leading to death
ssRNA
9.7
9
What is a cell that is infected by a virus, fungus, or bacterium?
What about a species that can be infected by a specific virus?
A host cell.
A host species.
What is the number of species and cell types that a virus or bacterium can infect?
Host range
For example, TMV is known to infect over 150 different species of plants while yellow fever caused by the flavivirus infects the brain and CNS.
What do viruses range in size from?
20 nm to 400 nm in diameter.
For size comparison, a bacterium is 1,000 nm in diameter while most eukaryotic cells is 10 to 1,000 times bigger than that of a bacterium.
Over 50 million adenoviruses (75 nm) could fit into an average-sized human cell.
All viruses have a protein coat enclosing a virus’s one or more molecules of nucleic acid (DNA or RNA) called a?
Capsid.
Capsids have a variety of shapes, including helical and polyhedral.
What are the subunits of a capsid called?
Capsomers
What are the several different protein subunits of a capsid called?
Capsomers
What type of structure does TMV have?
Helical capsid with identical capsomers.
What type of structure does the adenovirus have?
It is polyhedral, meaning 6 sided. The corners have protein fibers with a terminal knob at the end
What is a structure enclosing a viral capsid that consists of a membrane derived from the plasma membrane of the host cell and embedded with virally encoded spike glycoproteins?
Viral envelope
T/F Viral envelopes of influenza viruses are lipid bilayers to include all other viruses.
False. Typically yes for influenza viruses but some viruses may not have the viral envelope.
Although they help encasing and protecting the genetic material, what does the capsid and envelope also accomplish?
What helps viruses bind to the surface of a cell?
Enabling viruses to infect their hosts.
The protein fibers with a knob or spike glycoproteins.
What is a virus that infects bacteria?
Bacteriophages or phages.
They may have more complex protein coats, with accessory structures used for anchoring the virus to a host cell and injecting the viral nucleic acid
What is the genetic material of a virus?
The viral genome.
Answer the following questions on infections of the adenovirus.
- What plays an important role for the adenovirus’s ability to be accepted by the host cell?
- Why?
- Once connected via the CAR to the host cell, what process happens next?
- What forms to carry the virus but is then broken down by proteins provided by the viral capsid?
- Once released, what happens to the viral DNA?
- It’s capsid structure, primarily the protein fiber with a knob.
- The knob binds to a receptor on the host cell designated coxsackievirus and adenovirus receptor (CAR), because it can recognize either coxsackievirus or adenovirus.
- The adenovirus is taken into the host cell via receptor-mediated endocytosis.
- Vesicles
- During the breaking of the vesicles, the viral DNA makes it way to the nucleus and provides the information to make thousands of new viruses.