Viruses Overview

Genetic element that can multiply only in a living house

• Latin word for poison

Virus

What is the most abundant biological entity on earth?

Virus

What does a virus need for energy, metabolic, intermediates, and protein synthesis

Host cell

Viruses have their own ____ genome

Nucleic acid

A genetic element that contains either RNA or DNA surrounded by a protein capsid in that replicate only Inside host cells

Virus

The viral genome, surrounded by a protein coat, and sometimes other layers, which is the infectious virus particle

Virion

When was the first vaccine for rabies developed?

Late 1800s

What did Louis Pasteur hypothesize was the cause of rabies

A living thing, smaller than bacteria

What do people show that a disease tobacco was caused by a virus?

Dimitri ivanovski and martinus beijerinck

Who discovered an animal virus that causes foot and mouth disease in cattle

Loeffler and frosch

What did the early researchers find out about viruses through filtration?

When an infected liquid was filtered, it was still contaminated, which meant that it was contaminated with something smaller than bacteria

What is the first classical scenario of the origin of viruses?

Progressive hypothesis, a.k.a. escaped genes

What did the progressive hypothesis scenario predict?

Genetic fragments escaped from cells, and then entered into another cell to reproduce

What is the second scenario of the origin of viruses?

Regressive hypothesis

What does the regressive hypothesis predict?

Viruses evolved from complex organisms that lost genetic information over time in adopted a parasitic approach to replication

What is the third classical scenario of the origin of viruses?

Virus first

What does the virus first origin of viruses predict

Viruses existed before other organisms

What is the strong and weak evidence of the virus first hypothesis

Strong - The first replicating molecules consisted of RNA

Weak - The nucleus is a result of an Endo symbiotic like event of an envelope DNA virus

What is one of the main reasons viruses are not considered living

They are not cellular

When do viruses show traits of life, such as hereditary, development, and evolution

After they have attached to a living host

What do cells do to the genetic make up of the infected host cell?

Influence it

True or false, viruses have shaped away cells, tissues, bacteria, plants, and animals have evolved

True

What percentage of the human genome consist of sequences that come from viruses?

8%

What percentage of bacterial DNA contains viral sequences

10 to 20%

These parasites cannot multiply, unless they invade a specific wholesale, and instruct its genetic and metabolic machinery to make and release new viruses

Obligate, intracellular, parasites

How did the old system Classify animal, viruses

Based on their hosts and the diseases they caused

How does the new system classify animal viruses?

Based on the host and the disease they cause, structure, chemical composition, and similarities in genetic make up

How many families are not yet assigned to an order?

84

How much more viruses are there than bacteria and archaea combined?

10x

Viruses are ultra microscopic in size which ranges from…

20nm up to 1,000 nm in diameter

What is the basic structure of a virus?

A protein shell (Capsid) Which surrounds nucleic acid core

What two things can Nucleic acid be but not both

DNA or RNA

What on the viruses surface gives them high specificity for attachment to host cells

Molecules a.k.a. spikes

What do things does a virus lack?

Enzymes for metabolism and machinery for synthesizing proteins

How are viruses best observed

With special stains and electron Microscopy

What do viruses bear no resemblance to and lack any of the protein synthesizing machinery found in them

Cells

What are the three parts to the structure of a virus?

External Coating, Core containing nucleic acids, Matrix proteins and enzymes (Sometimes)

This is the protein shell that surrounds the genome of a virus

Capsid

This type of virus has no other layers

Naked virus

This virus has an outer layer consisting of a phospholipid bilayer and viral proteins

Enveloped virus

This is the nucleic acid and protein in envelope viruses

Nucleocapsid

Spikes can be found on what two types of viruses

Naked or envelope

What do spikes allow viruses to do?

Dock onto a host cell

This is the most prominent feature of a viral capsid, which Can be expressed as two primary types _____ And _____

Capsid

Helical

Icosahedral

What is a viral capsid made from

Capsomeres which spontaneously self assemble

This type of structure can only be found in the viruses that infect bacteria, and they are never envelope

Complex capsid structure

These types of Viruses take a bit of the cell membrane when they are released from a host cell

Enveloped viruses

What three locations can an envelope virus bud from?

Cell membrane, nuclear envelope, endoplasmic reticulum

An envelope virus is more flexible than the capsid, which means they are…

Pleomorphic

The sum total of the genetic information carried by an organism

Genome

In comparison to a cell, Viral genes are quite _____

Small

Why do cells have a larger genome than viruses?

It allows them to carry Out complex metabolic activity that’s necessary for independent life

What type of genes do viruses typically possess?

The ones needed to invade host cells

This type of virus is single-stranded or double stranded, which makes it linear or circular

DNA virus

This virus can be double stranded, but more often times it single stranded

RNA virus

Name the four types of RNA viruses based on the descriptions below

• Ready for immediate translation

• Must be converted before translation

• Individual genes exist on separate pieces of RNA

• Carry their own enzymes to convert RNA to DNA

• positive sense RNA

• Negative sense, RNA

• Segmented

• Retrovirus

What are the phases of the animal viral replication cycle?

• Adsorption

• Penetration

• Uncoating

• Synthesis

• Assembly

• Release

How long is the replication cycle?

Varies from 8 hours to 36 hours

What is the only way of virus can invade a host cell?

By making an exact fit with a specific host molecule

The limited range of cells that a virus can infect

Host range

What type of viruses affect the below systems?

• Liver cells of human

• Intestinal and nerve cells of primates

• Various cells of all mammals

• hepatitis B

• Poliovirus

• Rabies

What occurs during penetration and uncoating on the viral envelope with the host cell membrane?

Direct fusion - Envelope merges directly with the cell membrane

This process is when an entire virus is engulfed by the cell and enclosed in a vacuole or vesicle

Endocytosis

During the synthesis phase what type of Virus enters the host cells nucleus and is replicated and assembled there

DNA virus

During the synthesis phase what type of Virus is replicated and assembled in the cytoplasm

RNA virus

This phase is when the virus has put together using parts manufactured during the synthesis process

Assembly

this phase is the number of viruses released by infected cells, is viable controlled by the size of the virus and the health of the host cell

Release

what allows viruses to be shed gradually without the sudden destruction of the cell

Budding

This is when the cell harbors the virus, and is not immediately lysed and can last for a few weeks to the remainder of the hostels life

Carrier relationship

Viral DNA incorporated into the DNA of the host

Provirus

Periodically becomes activated under the influence of various stimuli like herpes

Chronic latent state

Because animal viruses can permanently alter genetic material what can it cause

Cancer

What is the name for cancer causing viruses

Oncogenic

What percentage of cancers are caused by viruses?

13%