Genetics of viruses and bacteria

Question 1

what are pathogens?

Answer 1

agents that cause disease symptoms in their hosts

Question 2

what are some general properties of virus?

Answer 2

a virus is a small nonliving particle with a nucleic acid genome enclosed in a protein, they are non-living.

Question 3

first virus discovered?

Answer 3

Tobacco Mosaic Virus (TMV)

Question 4

first human virus?

Answer 4

virus that causes yellow fever

Question 5

what is a cell that is infested by a virus called?

Answer 5

host cell

Question 6

what is host range?

Answer 6

number of species and cell types can be infected

Question 7

all viruses have a _____ (protein coat) that varies in shape and complexity

Answer 7

capsid

Question 8

capsids are composed of one or more protein subunits called?

Answer 8

capsomers

Question 9

capsids have a variety of shapes which are?

Answer 9

helical and polyhedral

Question 10

what helps viruses bind to their host cell?

Answer 10

glycoproteins

Question 11

what are bacteriophages?

Answer 11

viruses that infect bacteria

Question 12

when a virus infects a host cell, expression of viral genes leads to?

Answer 12

viral reproductive cycle

Question 13

what are the 5=6 common steps in a viral reproductive cycle?

Answer 13

Attachment, Entry, Integration (*), Synthesis of viral components, Viral assembly and Releases

Question 14

what is viral envelope derived from?

Answer 14

host cell plasma membrane

Question 15

what does integrase do?

Answer 15

Integrase cuts host chromosomal DNA and inserts viral genome

Question 16

what is phage in bacterial DNA called?

Answer 16

prophage

Question 17

what is the lysogenic cycle?

Answer 17

the phase of viral reproductive cycle when prophage is integrated into chromosome, no new phages made and prophage can be excised from bacterial chromosome to end the cycle

Question 18

what type of virus is HIV?

Answer 18

an RNA virus.

Question 19

once integrated, the viral DNA is a?

Answer 19

provirus

Question 20

viruses that follow the integration mechanism are?

Answer 20

retroviruses

Question 21

in HIV, the DNA provirus is not excised from host chromosome, but instead?

Answer 21

it is transcribed in the nucleus to produce many copies of viral RNA.

Question 22

what translates mRNA?

Answer 22

host cell ribosomes

Question 23

what does it mean when viruses self-assemble?

Answer 23

they spontaneously bind to each other to form a complete virus particle

Question 24

what are the two stages of assembly of HIV?

Answer 24

• Capsid proteins assemble around 2 molecules of viral RNA
  and molecules of reverse transcriptase and integrase
• Next the newly formed capsid acquires its outer envelope in a budding process

Question 25

Assembly of phage I requires the help of?

Answer 25

noncapsid proteins

Question 26

After phage assembly, a phage-encoded enzyme called ___?_____ digests the bacterial cell wall and causes the cell to burst

Answer 26

lysozyme

Question 27

why are steps 1,2,4,5 and 6 called the lytic cycle?

Answer 27

because they lead to cell lysis

Question 28

phages must ___?___ their host cell to escape

Answer 28

lyse

Question 29

latency is also called?

Answer 29

lysogeny

Question 30

Bacteriophages that can follow lysogenic or lytic cycle are?

Answer 30

temperate phages

Question 31

what is latency?

Answer 31

integration of genomes into a host chromosome

Question 32

___?___ phages only have lytic cycles

Answer 32

virulent phages

Question 33

what are episomes?

Answer 33

genetic elements
that replicate independently but occasionally integrate into host DNA

Question 34

what are the two different mechanisms of latency in human viruses?

Answer 34

• Virus integrates into host genome and may remain dormant for long periods of time e.g. HIV
• Other viruses can exist as episomes e.g. Herpes simplex type I and II, varicella zoster (chicken
  pox)

Question 35

latent is the same thing as?

Answer 35

inactive or resting form

Question 36

what are emerging viruses?

Answer 36

emerging viruses are ones that have arisen recently or have recently become more infectious, typically result from mutation in pre-existing viruses

Question 37

list some examples of emerging viruses

Answer 37

coronavirus, new strains of influenza, zika virus, HIV/AIDS

Question 38

what is a pandemic?

Answer 38

disease that occurs over a wide geographic area and affects a high proportion of the human population

Question 39

what does H1N1 cause?

Answer 39

swine flu

Question 40

what type of white blood cell does aids destroy?

Answer 40

helper T cell

Question 41

what is regressive evolution in virus origin?

Answer 41

viruses are degenerate cells that have retained the minimal genetic information for replication

Question 42

what are viroids?

Answer 42

they are composed solely of a single-stranded circular RNA molecule a few hundred nucleotides in length, infects plant cells and RNA genome does not code for protein

Question 43

Prions

Answer 43

composed entirely of protein, converts normal protein to abnormal form

Question 44

several types of neurodegenerative diseases of human and livestock

Answer 44

group of diseases called transmissible spongiform encephalopathies (TSE)
E.g. Scraple (disease of sheep and pigs characterized by intense itching followed by neurodegeneration), Mad cow disease (begins with changes in posture and temperament, followed by loss of coordination and neurodegeneration), Chronic wasting disease (a disease of seer and rocky mountain elk which symptom is weight loss over time, it is progressive and fatal)