Lecture 1

Question 1

virion

Answer 1

• complete virus particle outside of the host cell
• the infectious virus particle

Question 2

Virion consits of…

Answer 2

• nucleic acid genome (either RNA or DNA)
• protective protein coat (capsid)
• sone contain a lipid envelope

Question 3

envelope or viral membrane

Answer 3

host-cell derived lipid bilayer carrying viral glycoproteins

Question 4

nucleocapsid or core

Answer 4

the nucleic acid-protein assembly packaged within the virion

Question 5

capsid or coat

Answer 5

the protein shell surrounding the nucleic acid genome

Question 6

structural unit or asymmetric unit

Answer 6

unit from which capsids or nucleocapsids are built

Question 7

subunit (protein subunit)

Answer 7

single, folded polypeptide chain

Question 8

viruses may lack essential function such as…

Answer 8

• synthesis of basic biological building blocks ex. nucleotides, lipids
• generation of useable chemical energy (ATP)
• protein synthesis machinery

Question 9

once inside the host cell…

Answer 9

• virus particles disintegrate/break down (uncoating)
• release genetic material inside the cell
• synthesize mRNAs and viral proteins
• then direct replication of viral genome using host machinery
• viral structural proteins encapsidate newly replicated genome which creates virus particles

Question 10

viral genome

Answer 10

• can be either DNA or RNA (not both)
• single stranded, double stranded, circular

Question 11

4 major characteristics used in virus classificatio

Answer 11

1. type of genome (RNA or DNA)
2. symmetry of capsid
3. presence or absence of envelope
4. dimensions

Question 12

+ve strand

Answer 12

encodes for a protein

Question 13

-ve strand

Answer 13

complementary strand

Question 14

RNA viruses

Answer 14

• only known forms of life that can have RNA genomes
• most encode their own RNA-dependent RNA polymerases

Question 15

2 main issues of having a RNA genome

Answer 15

1. mRNA must be synthesized from an RNA template, instead of DNA template
2. RNA genome must be replicated
   - problematic because the host cell does not have machinery to do it

Question 16

Retrovirus genome

Answer 16

• have RNA genome
• gets converted to RNA by host cell using reverse transcriptase encoded by the viral genome
• produces a complementary DNA copy of the RNA
• the DNA copy is then inserted into the DNA of the host cell

Question 17

Why study viruses?

Answer 17

• can infect all forms of life
• important disease-causing agents in humans
• most abundant biological entities
• play a critical role in various ecosystems, disease and are an excellent tool for understanding the biology of cellular processes

Question 18

Discoveries from the study of viurses

Answer 18

1. DNA carries inherited genetic info
2. Identification of promoters for eukaryotic RNA polymerase
3. Enzymes involved in cellular DNA replication
4. RNA splicing in eukaryotic cells
5. Isolation of numerous cellular oncogenes and the understanding that cancer is caused by their mutation or unregulated expression

Question 19

Hershey and Chase Experiment

Answer 19

• showed that DNA carries genetic information
• infected cells with bacteriophages and looked at progeny
• found that when DNA was labelled, lots of the radioactivity was transferred to the progeny
• when protein was labeled, barely any radioactivity transferred

Question 20

Filtration and tobacco mosaic virus

Answer 20

• viruses were distinguished from other microorganisms by filtration
• filtered sap of infected plants
• the filter kept bacteria from going through
• injected what was filtered into other plants and it was able to infect them
• implied that the infectious agent was smaller than bacteria

Question 21

crystallization of tobacco mosaic virus

Answer 21

• provided the first solid evidence that viruses were physical entities made up of specific chemical components
• challenged conventional notions about genes and the nature of living things
• found that highly purified TMV forms crystals
• lead to the question: Are viruses alive?