Biodiversity - Viruses

Question 1

viruses are…

Answer 1

composed of genetic material (DNA or RNA) surrounded by protein and lipid bilayer, no organelles, don’t metabolize, can’t reproduce on their own (need host cell for replication)

Question 2

what are viruses

Answer 2

Super small infectious agent that can only reproduce in a host cell

Question 3

what form do viruses take when they are not invading a host

Answer 3

crystalline form

Question 4

2 hypotheses as to where viruses came from

Answer 4

1. could be runaway stretches of nucleic acid from a larger organism that detached and became active, so new viruses are forming frequently and many don’t have ancestors
2. once lived outside of host cells, but over time due to their parasitic lifestyle, they lost the genes necessary to live outside the host

Question 5

what types of organisms can viruses infect

Answer 5

anything that is cellular (plants, animals, bacteria) but they are very species specific

Question 6

viruses that affect bacteria

Answer 6

bacteriophage or simply phages

Question 7

Structure of virus

Answer 7

genetic material, either DNA or RNA
a protective layer known as a capsid
lipid envelope from host cell’s membrane

Question 8

caspid

Answer 8

protein covering that surrounds a virus

Question 9

lipid envelope

Answer 9

protective outer covering of a virus that comes from the host cell’s membrane when it exits

Question 10

viruses are classified based on

Answer 10

1. type of nucleic acid (DNA or RNA)
2. single stranded or double stranded
3. whether or not they use reverse transcriptase (works backwards going from RNA to DNA)

Question 11

dogma theory

Answer 11

information in a cell flows from DNA to RNA to protein

Question 12

reverse transcriptase

Answer 12

an enzyme in viruses that have RNA which changes RNA back into DNA

Question 13

3 types of viruses

Answer 13

DNA, RNA, retrovirus

Question 14

retroviruses definition

Answer 14

A retrovirus is an RNA virus, but instead of inserting the RNA directly into the cell, it first converts it into DNA

Question 15

DNA viruses

Answer 15

genome is double stranded DNA (dsDNA), new strains are rare, immune system always recognizes the virus, can carry both lytic or lysogenic cycle. Example smallpox, chicken pox

Question 16

RNA viruses

Answer 16

single stranded RNA (ssRNA), mutation is permeant, new strains are common, immune system might not recognize new mutated virus, new antibodies need to be made. Can’t carry the lysogenic cycle since RNA can’t hide in a DNA. Example rubella virus which causes German Measles

Question 17

Retroviruses

Answer 17

can carry out lysogenic cycle, more dangerous than DNA and RNA, can mutate, can lay dormant. Example HIV which causes AIDS

Question 18

Viruses function

Answer 18

invade host cell and start reproducing

Question 19

host range

Answer 19

viruses can infect only a limited # of hosts.

Question 20

how do viruses identify their hosts

Answer 20

by a “lock and key” fit between proteins on the outside of the virus and receptor molecules on the surface of the host

Question 21

2 cycles for virus reproduction

Answer 21

Lytic cycle and Lysogenic cycle

Question 22

lytic cycle

Answer 22

infects host and makes more viruses. when their are many viruses they break open the host cell. the new viruses then infect more host cells

Question 23

lysogenic cycle

Answer 23

viruses coexist with cell for a period of time ‘hidden’ in host genome. virus gets replicated every time host cell replicates. eventually enters lytic cycle after a period of incubation

Question 24

Lytic cycle steps

Answer 24

1. attachment: attaches to the host
2. entry: inserts its DNA into host cell, protein coat remains outside or may enter host cell
3. replication: viral genome takes over host cell, destroys host DNA and uses host machinery to make copies of its own genome and protein coat
4. Assembly: virus parts are assembled together
5. lysis and release: new virus particles rupture/lyse the host cell. host cell dies

Question 25

onset of symptoms of lytic cycle

Answer 25

almost immediately

Question 26

how long does it take for a virus to reproduce with the lytic cycle

Answer 26

about 30 mins and produces up to 200 new viruses

Question 27

Lysogenetic cycle onset of symptoms

Answer 27

delayed

Question 28

What causes symptoms of disease

Answer 28

destruction of the host cell

Question 29

more virulent

Answer 29

less chance for transmission

Question 30

less virulent

Answer 30

more chance for transmission

Question 31

restriction endonucleases

Answer 31

enzymes used by bacteria that recognize and cut foreign DNA or RNA

Question 32

how do bacteria kill viruses

Answer 32

successful restriction enzymes may kill virus but bacteriophages that develop resistance to the endonucleases end up killing the bacteria

Question 33

antibiotics kill bacteria but …

Answer 33

don’t kill viruses

Question 34

how can humans prevent viral invasions

Answer 34

antiviral drugs or can be immunized by vaccines

Question 35

vaccines

Answer 35

contains non-infectious virus particles or a weakened strain of virus, causes the body to make antibodies against the virus so it is ready to fight the infection when the real virus invades

Question 36

what are viruses used for

Answer 36

to study the basic mechanisms of molecular biology like DNA replication, protein synthesis, geneticists use to genetically modify organisms

Question 37

Virotherapy

Answer 37

use of viruses to treat bacterial diseases (by killing bacterial diseases) and some forms of cancer (by killing cancer cells

Question 38

Prions

Answer 38

not viruses, don’t contain genetic material, proteins found in our bodies

Question 39

results in disease when prions …

Answer 39

convert from their normal shape into a different shape but also maintain their chemical composition

Question 40

Viable vectors (carries) that can deliver a gene to target cells

Answer 40

gene therapy