BIO 3 7 FIN

Summary

This video explores the fascinating world of subviral particles, including viroids, prions, and satellite viruses, shedding light on their unique biological properties. Viroids, made solely of RNA, infect plant cells, while prions, composed of misfolded proteins, cause devastating neurodegenerative diseases in humans and animals. The video also delves into satellite viruses that depend on other viruses (helper viruses) for replication. Through examples like potato spindle tube viroid and bovine spongiform encephalopathy (mad cow disease), the video emphasizes the complexity and intrigue of these microscopic agents, highlighting their potential dangers and their impact on living organisms.

Takeaways

• 😀 Viroids are simple infectious particles made only of RNA, without a protein coat, unlike viruses.
• 😀 Viruses, which are more complex than viroids, consist of protein capsids and genetic material, and they rely on host cells to replicate.
• 😀 Viroids can cause plant diseases, such as potato spindle tube viroid (PSTVD), which affects the growth of potatoes.
• 😀 Prions are proteins that can cause diseases by inducing normal proteins to fold abnormally, which can lead to brain damage in animals and humans.
• 😀 Prions do not contain genetic material, unlike viruses and viroids, and propagate by changing the shape of other proteins.
• 😀 Some prion diseases include mad cow disease (BSE), scrapie in goats, and kuru in humans, which can take decades to show symptoms.
• 😀 Satellite viruses, like hepatitis D, require a helper virus (like hepatitis B) to replicate, and they cannot replicate on their own.
• 😀 Satellite viruses are different from regular viruses because they depend on another virus to reproduce.
• 😀 Virophages are a type of satellite virus that can parasitize helper viruses, like Sputnik, by hindering the replication of the helper virus.
• 😀 The complexity of viruses, viroids, and prions showcases the amazing diversity of biological agents that can infect and affect living organisms.

Q & A

What is the main difference between viruses and viroids?

The main difference between viruses and viroids is that viruses are composed of a protein capsid and genetic material (RNA or DNA), whereas viroids consist only of RNA without a protein coat. Viroids are simpler and do not require ribosomes for replication.

How do viroids infect host cells?

Viroids infect host cells by taking over the function of RNA polymerase within the host cell to replicate. However, unlike viruses, viroids do not use the host's ribosomes to synthesize proteins.

Can viroids affect human cells?

No, viroids only infect plant cells. They do not infect human cells or animals.

What are some examples of viroids and the diseases they cause?

Examples of viroids include Potato Spindle Tube Viroid (PSTVD), which affects potato plants, Apple Scar Skin Viroid (ASSVD), which causes spots on apple skins, and Avocado Sunblotch Viroid (ASBVD), which reduces avocado yields.

What is the structure of a prion, and how does it cause disease?

A prion is composed solely of misfolded protein and does not contain genetic material. Prions cause disease by inducing normal proteins to adopt abnormal shapes, which leads to the aggregation of these proteins and the degeneration of affected tissues, particularly in the brain.

What diseases are caused by prions?

Prion diseases include Bovine Spongiform Encephalopathy (Mad Cow Disease) in cattle, Scrapie in sheep, Kuru and Creutzfeldt-Jakob Disease in humans, all of which primarily affect the nervous system.

How do prions spread from one organism to another?

Prions can spread through the consumption of infected tissue, such as eating prion-infected beef. The prions then cause disease by altering the shape of proteins in the new host.

What makes prion infections difficult to diagnose?

Prion infections are difficult to diagnose because they do not cause symptoms until years after the initial infection. By the time symptoms appear, significant neurological damage has already occurred.

What is a satellite virus, and how does it differ from regular viruses?

A satellite virus is a type of virus that cannot replicate on its own and requires the presence of another virus (known as a helper virus) for replication. Unlike regular viruses, satellite viruses do not have all the necessary genes for self-replication.

What is the relationship between hepatitis D and hepatitis B?

Hepatitis D is a satellite virus that requires the presence of hepatitis B to replicate. Hepatitis D cannot infect or replicate in a host without hepatitis B, making it dependent on the helper virus.