Lecture 15: Introduction to Viruses Flashcards
Tuesday 12th November 2024
Is it true that we carry viral genetics as part of our own genetic materials?
yes, but these viruses are not pathogenic. They are remnants of viral infections that occurred in our distant evolutionary past.
What percentage of our genome encodes for proteins?
1.5%
What was the first virus to be identified?
Tobacco Mosaic Virus (TMV)
What is the first written record of a viral infection?
The first written record of a virus infection is shown in hieroglyph from Memphis, drawn in approximately 3700BC, which depicts a temple priest called (Ruma) showing typical clinical signs of paralytic poliomyelitis.
Why is it thought that Pharaoh Rameses died of smallpox?
Because pox marks were found on his mummy
Who developed the first ever vaccine?
Edward Jenner. He developed the smallpox vaccine
Which 3 scientists contributed to the development of the concept of viruses?
Dmitri Iwanowski, Martinus Beijernick, andHelmut Ruska
What did Dmitri Iwanowski demonstrate? (1892)
That extracts from infected tobacco plants could transmit disease to other tobacco plants
How did Dmitri Iwanowski come to the conclusion that extracts from infected tobacco plants could transmit disease to other tobacco plants? (1892)
- He took an extract from infected tobacco leaves and filtered it through a porous filter (a Chamberland filter) designed to retain bacteria. The filter used had pores small enough to trap bacterial cells, which were the suspected culprits at the time.
- Iwanowski then sprayed healthy plants with the filtered liquid.
- Surprinsingly, the healthy plansts became infected with TMV, despite the filtrate being free of bacteria.
- This suggested that the disease-causing agent was smaller than bacteria and could pass through the pores of the filter.
- He concluded that TMV was an infectious disease, and that the pathogen that caused TMV must be smaller than a bacterium.
- He did not take his work any further
What did Dutch microbiologist, Martinus Beijernick , do in 1898?
- He confirmed the same findings as Iwanoski and showed that the filtrate contained a new form of infectious agents.
- He also demonstrated that the agent only multiplied living, dividing cells because the filtrate retained infectivity even after dilution. He used the term filtrable agent to describe it
Who is considered the father of virology?
Martinus Beijernick
What did Loeffler & Frosch do in 1898?
They repeated the TMV experiments and demonstrated Foot and Mouth Disease in cattle was caused by similarly small infectious agents, Foot and Mouth Disease Virus ( FMDV)
What did Carlos Finlay do in 1901?
- He was a Cuban physician who conducted research indicating that mosquitoes were the cause of yellow fever.
What and when was the first human virus to be discovered?
The yellow fever virus in 1901
When was the yellow fever virus discovered?
In 1901
When was the rabies virus first discovered?
In 1903
when was the Variola virus first discovered?
In 1906
When was the poliovirus first discovered?
In 1908
When was the Rous sarcoma virus (chickens) first discovered?
In 1911
When were bacteriophages first discovered?
In 1915
When was the influenza virus first discovered?
In 1933
When is a phage produced?
When a virus infects a bacteria
When was the first electron microscope developed and by whom?
The first electron microscope was first discovered in 1933 by Ernst Ruka
When and who first showed an EM image of a bacteriophage and TMV?
Helmut Ruka in 1939
When was the name filtrable dropped and replaced by the term virus?
In 1939
What is the size range of viruses?
20-300nm
Why aren’t larger viruses an issue?
because they only infect parasites, not humans
What are the 5 key features of viruses?
- They’re small in size (20-300nm)
- They contain either DNA or RNA, but no chromosomes
- Have a different replication strategy to bacteria, do not replicate via binary fission
- They are obligate intracellular parasites, and so can only replicate and carry out their life cycle inside the cells of a host organism.
- Have a simple structure
Why do we study viruses?
To understand viral diseases
To develop therapeutics
To design measures to reduce viral transmission
