Viruses Flashcards

Question

Describe DNA viruses + their replication

Answer 1

Categorized by - Their genomic structure - Presence of an envelope - Size and shape of their capsid - The host cells they attack 3 types - dsDNA → virus can follow normal replication flow (DNA → RNA → protein) - ssDNA → host enzymes are used to synthesize a complementary strand to genome strand, thus producing dsDNA which can then follow normal replication flow - dsDNA-RT (double stranded DNA retroviruses)

Answer 2

Only infective agents that store genetic information in RNA molecules Categorized by - Their genomic sequence - Presence of envelope - Size and shape of their capsid 4 types: - +ssRNA → acts like mRNA, can be translated directly to make viral proteins - RNA retroviruses (+ssRNA that convert their genome to DNA) - (–ssRNA) → cannot translate until replicated into +ssRNA by RNA dependent RNA polymerase (RdRP) - dsRNA → uses –ssRNA as template to replicate +ssRNA - Positive RNA acts like mRNA (can be used by a ribosome to translate protein) - Negative RNA must first be transcribed as mRNA to be processed by a ribosome (Requires viral RNA-dependent RNA polymerase)

Answer 3

- Zoonoses (learning objective in itself so know this) Diseases naturally spread from animal host to humans EX: rabies, black plague, lyme disease, west nile virus Acquire zoonoses through various routes Direct contact with animal or its waste Eating animals Bloodsucking arthropods Humans are usually dead-end host to zoonotic pathogens

Answer 4

Lytic is where the viral proteins are being produced and then the lyse and rupture. lysogenic is just replication of genetic material and it later excises itself once it goes into the lytic Lytic replication: -Replication cycle that usually results in death and lysis of host cell Stages: - Attachment - Entry - Synthesis - Assembly - Release (Phage injects its DNA into cytoplasm and directs the synthesis of many new phages. THe cell lyses and releases the new phages. New phages can then bind to bacterial cells) Lysogenic replication: The phage DNA injects its DNA into the cytoplasm of the bacterial cell. The phage DNA integrates into the host chromosome. Then the prophage DNA is copied when the cell divides. Exposure to stress such as UV light triggers excision from the host chromosome. (viral proteins are not being replicated in bacteriophages???) Infected host cells grow and reproduce normally for generations before it lyses Viral genetic material is integrated into the chromosome

Answer 5

DNA viruses Categorized by Their genomic structure Presence of an envelope Size and shape of their capsid The host cells they attack 3 types: dsDNA → virus can follow normal replication flow (DNA → RNA → protein) ssDNA → host enzymes are used to synthesize a complementary strand to genome strand, thus producing dsDNA which can then follow normal replication flow dsDNA-RT (double stranded DNA retroviruses) RNA viruses Only infective agents that store genetic information in RNA molecules Categorized by Their genomic sequence Presence of envelope Size and shape of their capsid 4 types: dsRNA → uses –ssRNA as template to replicate +ssRNA +ssRNA → acts like mRNA, can be translated directly to make viral proteins –ssRNA → cannot translate until replicated into +ssRNA by RNA dependent RNA polymerase (RdRP) RNA retroviruses (+ssRNA that convert their genome to DNA)

Answer 6

( be able to expand on each step this is only the skeletal structure) Animal Viruses - Replication - Attachment - Synthesis - Assembly and release Latency of animal viruses bacteriophages - attachment - replication - synthesis - assembly and release

Answer 7

Latency: - Viruses remain hidden or dormant inside host cell which cause latent infections - May cause an acute infection before becoming dormant - Ex: varicella zoster virus causes chickenpox (affects many areas of the body) but 10-12 days later becomes dormant and stops replicating → after many years of dormancy the virus is reactivated and causes shingles (nerve cell specific) - Latent viruses may remain dormant by existing as circular viral genome molecules outside of host chromosome or by becoming proviruses by integrating into host genome Inclusions and oncogenesis: Inclusions: - Aggregates of proteins found in neurons - Caused by the presence of viruses - Represent sites of viral multiplication - Occur in the cytoplasm Oncogenesis: - Process of normal cells turning into cancer cells - Activation of oncogenes - Series of genetic and cellular changes - Cells divide in uncontrolled manner - Cancer causing

Answer 8

- Oncogenesis allows viruses to encode for proteins that break down the host cell genome and prevent cell death which leads to uncontrolled cell growth. - Oncogenes are a gene that when activated have the potential to cause cancer because they are pleiotropic and can regulate growth, apoptosis, differentiation, cell cycle, and cell proliferation. ----Metastasis: spread of cancerous cells throughout the body ----Benign: tumor remains in place -----Malignant: abnormal growth of neoplastic cells - form lump of tissue ( look at blue on the doc for more info)

Answer 9

Culturing viruses in mature organisms: 1. In bacteria 2. In Plants and animals In embryonic chicken eggs: 1. Inexpensive 2. among the largest of cells 3. Free of contaminating microbes 4. Contain nourishing yolk In cell tissue culture: 1. Consists of cells isolated from an organism and grown on a medium or in a broth 2. Two types of cell cultures: a. Diploid cell cultures b. Continuous cell cultures Visualize Cells 1. Plaque assays: a. Dilutions of virus preparation made and plated on lawn of host cells b. Number of plaques counted c. Results expressed as plaque-forming units (PFU) / mL 2. Viral plaques: a. Viral plaques in a lawn of bacterial growth

Answer 10

Viroid: A subviral particle lacking a capsid and consist solely as RNA a. extremely small, circular pieces of RNA that are infectious and pathogenic in plants b. Similar to RNA viruses, but lack capsid c. Do not encode gene products d. May appear linear due to H bonding Virusoid: A subviral particle lacking a capsid, consist solely as RNA, and requires a virus for replication a. Infectious agents composed only of closed, circular ssRNAs b. Do not encode gene products c. Requires virus helper d. Requires host cell DNA-dependent RNA polymerase to replicate e. Cause plant diseases → found in nucleolus or chloroplasts; disease caused by RNA silencing Prion: A misfolded, infectious protein, only affecting the brain - Proteinaceous infectious agents ( interacts with another protein and causes it to misfold which then interacts with another protein causing it to misfold = domino effect) changes in weak chemical interactions through protein protein interactions) - Cellular PrP protein a. Made by all mammals b. Function unknown c. Normal structure with a-helices called cellular PrP Prion PrP -Disease-causing form with B-sheets called prion PrP Prion PrP converts cellular PrP into prion PrP by inducing conformational change These compare to viruses and other organisms in the way that they only consist of either RNA or proteins whereas viruses and other organisms can consist of DNA and RNA and proteins all in one.

Answer 11

No viruses are not alive because they do not meet all the requirements (cannot carry out metabolic pathways and cannot reproduce independently and require a host) Others consider them to be the least complex living entities because they: a. Use sophisticated methods to invade cells b. Have the ability to take control of their host cells c. Are able to replicate themselves Others think it's a complex pathogenic chemical that lacks characteristics of life Characterics of life: Growth Metabolism Responsiveness Reproduction Cell Structure Viral infection leads to morbidity and mortality: Viruses cause 20-25% of human cancers Some carry copies of oncogenes as part of their genomes Some promote oncogenes already present in host Some interfere with tumor repression when inserted into hosts repressor gene Specific viruses are known to cause 15% of human cancer Once viral infections invade a host cell they can begin to replicate and destroy more and more cells They can also activate oncogene which could cause uncontrolled cell growth.