Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Lichens are symbiotic associations, consisting of an algal component () and a fungal component (). The alga prepares food while the fungus provides shelter and absorbs mineral nutrients and water.
Viruses are non-cellular organisms characterized by having an inert crystalline structure outside the living cell. They are obligate parasites.
The genetic material of a virus can be either or , but never both. Generally, plant viruses have single-stranded (), while animal viruses have either , double-stranded (), or double-stranded ().
The protein coat of a virus is called the , made of small subunits called , which protects the nucleic acid.
Viroids were discovered by in . They are smaller than viruses, lack a protein coat, and contain free of low molecular weight.
Prions are infectious agents composed of abnormally folded proteins. They are similar in size to viruses and cause neurological diseases like Bovine Spongiform Encephalopathy () and Cr-Jacob disease ().
Lichens are very good pollution indicators; they do not grow in areas polluted with sulfur dioxide ().
📐Formulae
💡Examples
Problem 1:
Who demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and what was the fluid called?
Solution:
(); the fluid was called .
Explanation:
This term translates to 'infectious living fluid', highlighting the infectious nature of the pathogen (Tobacco Mosaic Virus) which was smaller than bacteria as it passed through bacteria-proof filters.
Problem 2:
Differentiate between a Virus and a Viroid based on their structural components.
Solution:
A virus consists of genetic material ( or ) enclosed in a protein coat (), whereas a viroid consists only of free without any protein coat.
Explanation:
This distinction was established when found that the agent causing potato spindle tuber disease lacked the proteinaceous shell found in traditional viruses.
Problem 3:
A scientist finds an infectious agent that causes the 'Mad Cow Disease'. Upon analysis, it contains only protein and no detectable nucleic acid. Identify the agent.
Solution:
The agent is a .
Explanation:
Prions are unique pathogens because they lack a genome made of or and instead propagate by inducing normal proteins to misfold into the infectious form.