virus

Question 1

two main classes of viruses

Answer 1

RNA viruses and DNA viruses
contain RNA / DNA as their genetic material

Question 2

types of RNA / DNA viruses

Answer 2

RNA: single / double stranded

DNA: single-stranded, single stranded circular
double stranded, double stranded circular, w/ covalently sealed ends, w/ covalently linked terminal protein

Question 3

four steps in the virus lifecycle

Answer 3

disassembly of infectious virus particle
replication of viral genome
synthesis of viral proteins by the host cell translation machinery
reassemble of components into progeny virus particles

Question 4

justification for why viruses are not alive

Answer 4

incapable of carrying out all life processes:
- not made of cells
- cannot reproduce independently - no protein synthesis machinery
- do not grow / undergo division
- do not transform energy

Question 5

define capsid

Answer 5

the protective protein coat surrounding the nucleic acid / viral genome in a virus

Question 6

what is the nucleocapsid?

Answer 6

the capsid along with the enclosed viral genome

Question 7

structure and features of an enveloped virus

Answer 7

enveloped viruses exit a host cell by budding from it (not killing cell), acquiring a lipid bilayer membrane enclosing the nucleocapsid

Question 8

difference between enveloped and non enveloped viruses

Answer 8

non-enveloped virus leaves cell by lysing it (vs enveloped leaves by budding)
enveloped = persistent infections

Question 9

despite the variety, all viral genomes encode for three types of proteins:

Answer 9

proteins for replicating the genome, proteins for packaging + delivering the genome, proteins that modify the structure/function of HOST cell to enhance replication

Question 10

define bacteriophage

Answer 10

viruses that infect bacteria

Question 11

virus extracellular vs intracellular state

Answer 11

extracellular: called a virion, has capsid, some have phospholipid envelope

intracellular: capsid removed, virus exists as nucleic acid (Genetic material)

Question 12

name some general virus uncoating strategies

Answer 12

fusion (eg. enveloped, HIV)
receptor-mediated endocytosis, entering as an endosome
pore-forming (eg. poliovirus)

Question 13

define error-prone replication

Answer 13

often RNA viruses exploit error prone replication as a strategy to evade the host immune system
results in diversification and related strains of viruses

Question 14

define zoonotic transfer

Answer 14

infectious disease transmitted between species

Question 15

describe the structure of SARS-CoV-2

Answer 15

single-stranded RNA genome approx 30,000 nucleotides long, packages with an RNA binding protein and enclosed by a lipid bilayer envelope

Question 16

main features of the replication cycle of SARS-CoV-2

Answer 16

the use of a coronavirus-specific RNA polymerase to make copies of its genome

synthesises a complementary RNA, used to produce mRNAs for viral proteins and also acts as a template for synthesis of new viral genomes
the two components assemble

Question 17

how is covid detected?

Answer 17

with PCR
amplifies the signals from nucleic acid
involves gel electrophoresis