Lecture 18- Viruses

Question 1

virus

Answer 1

infectious particle consisting of genes packaged in a protein coat; sometimes may have an outer envelope or membrane; require host to replication (obligate, intracellular parasites)

Question 2

origin of viruses

Answer 2

progressive, regressive, virus-first hypothesis

Question 3

progressive/escape hypothesis

Answer 3

viruses arose from genetic elements that gained the ability to move between cells

Question 4

regressive/reduction hypothesis

Answer 4

viruses are remnants of cellular organisms

Question 5

virus-first hypothesis

Answer 5

viruses predate or coevolved with their current cellular hosts

Question 6

characteristics of a virus

Answer 6

host, genome, capsid, envelope

Question 7

viral genomes

Answer 7

DNA or RNA (double or single stranded), single linear or circular molecule of the nucleic acid

Question 8

capsid

Answer 8

protein shell that encloses the viral genome, built from proteins capsomeres

Question 9

viral envelopes

Answer 9

derived from host cell membranes, surround capsid of influenza viruses

Question 10

bacteriophages/phages

Answer 10

elongated capsid head that encloses their DNA and a protein tail piece attaches the phage to the host and injects the phage DNA inside

Question 11

host range

Answer 11

a limited number of species a virus can infect; broad or small;

Question 12

central dogma an viruses

Answer 12

take advantage of central dogma

Question 13

viral replication

Answer 13

1. recognition of host cell and attachment, entry 2. genome replication and. protein synthesis 3. viral mRNA is produced and viral proteins are made using host ribosomes 4. assembly, new viral genomes associate with capsid proteins 5. release, mature virions leave the cell

Question 14

lysogenic cycle

Answer 14

replicates the phage genome without destroying the host; viral DNA is incorporated into the host cell’s chromosome

Question 14

temperate phage

Answer 14

phages that use both the lytic and lysogenic cycles; lambda

Question 15

lytic cycle

Answer 15

a phage replicative cycle that culminates in the death of the host cell; produces new phages and lyses (breaks open host’s cell wall), releasing progeny viruses

Question 16

virulent phage

Answer 16

a phage that reproduces oonly by the lytic cycle

Question 17

classifying viruses that infect animals

Answer 17

an RNA or DNA genome, either single or double stranded, and the presence or absence of a membraneous envelope

Question 18

retroviruses

Answer 18

use reverse transcriptase to copy their RNA genome into DNA (HIV); RNA polymerase transcribes the provirus DNA into RNA molecules for synthesis of viral proteins and release genomes for new virus particles

Question 19

provirus

Answer 19

the viral DNA that is integrated into the host genome, PERMANENT resident of host cell

Question 20

CRISPR-Cas system

Answer 20

prokaryotic defense, based on sequences called clustered regularly interspaced short palindromic repeats (make loop structure)

Question 21

“spacer sequence”

Answer 21

corresponds to DNA from a phage that previously infected the cells

Question 22

CRISPR-associated (cas) proteins

Answer 22

nuclease proteins that interact with the CRISPR region; use phage related RNA to target the invading phage DNA; phage DNA is cut and destroyed;

Question 23

relationship between phage and bacteria

Answer 23

in constant evolutionary flux; natural selection favors phage mutants that can bind to altered cell surface receptors or that are resistant to enzymes

Question 24

adaptive immune response

Answer 24

response to a specific pathogen; only present in vertebrates; recognizes very specific part of pathogen; produces antigen proteins

Question 25

immune system

Answer 25

keeps the internal body free of disease causing microbes/pathogens in mammals

Question 26

outside replicating pathogens

Answer 26

bacteria and fungi

Question 27

inside replicating pathogen

Answer 27

viruses

Question 28

3 major lines of defense

Answer 28

1. barriers (physical, chemical, biological) 2. innate immune system 3. adaptive immune system

Question 29

innate immune system

Answer 29

operates constantly, innate (skin, mucus membranes, enzymes, etc.); not affected by prior exposure, not directed specifically to a particular infectious agent

Question 30

innate vs adaptive immunity

Answer 30

LOOOKKKK

Question 31

pattern recognition receptors (PRRs)

Answer 31

present on host cells and recognize microbes; viral PRRs inside cell

Question 32

pathogen-associated molecular patterns (PAMPs)

Answer 32

PRRs bind to these structures unique to mircobes and they signal immune response to pathogen, external or internal

Question 33

PRR binds to PAMP

Answer 33

recognize PAMPs, produce cytokines to communicate infection to other cells

Question 34

cytokines

Answer 34

diffuse to other cells and bind to cytokine receptors to transmit signal

Question 35

anti-viral response

Answer 35

PAMP is intercellular

Question 36

interferon response

Answer 36

PAMP is intracellular; interfere with infection, stop making new viruses, neighboring cells aren’t producing resources, gives innate immune cells an opportunity to respond, buys time

Question 37

T cells and B cells

Answer 37

thymus and bone marrow; white blood cells adaptive immune system relies on; both bind to antigens via antigen receptors; remain dormant but infection is checked by 100s of them

Question 38

pathogen specific

Answer 38

each individual B or T cell is specialized to recognize a specific type of molecule

Question 39

epitopes

Answer 39

regions on the surface of antigens that have complementary shapes to antigen binding sites

Question 40

colonial expansion

Answer 40

when a B or T cell is selected and starts to divide; creates army of clones to fight infection

Question 41

plasmas cells

Answer 41

create and release antibody

Question 42

memory cells

Answer 42

persist in body and wait for pathogen to enter again

Question 43

immunological memory

Answer 43

responsible for long-term protections against diseases, due to prior infection or vaccination

Question 44

primary immune response

Answer 44

first exposure to a specific antigen; selected B and T cells give rise to their effector forms

Question 45

secondary immune response

Answer 45

memory cells facilitate a faster, more efficient response