Microbiology

Question 1

viruses can survive without a host, true or false

Answer 1

false

Question 2

the main components of a virus

Answer 2

the genetic material
the protein coat(capsid)
the lipid membrane in some viruses (the envelope)
glycoproteins

Question 3

some example of DNA viruses

Answer 3

poxyvirus
adenovirus
parovirus
papiloma virus
herpes

Question 4

some example of RNA viruses

Answer 4

HIV
rotavirus
influenza
rabies…etc

Question 5

permissive cells

Answer 5

these are cells that a virus may use to replicate

note that viruses can only infect certain species and certain cells within that species

Question 6

what is molecularly required to be present on the host cell for a virus to be able to infect it

Answer 6

a viral receptor

Question 7

bacteriophage

Answer 7

type of virus that infects and replicates in a bacteria

Question 8

the virus that causes covid-19

Answer 8

SARS-CoV-2

aka 2019-nCOV

Question 9

simply state the stages involved in viral infection

Answer 9

attachment,
penetration,
uncoating
replication,
assembly,
release

Question 10

viruses are described as?

Answer 10

obligate intracellular parasites, meaning they must live and replicate inside a host cell

Question 11

the function of interferons

Answer 11

they interfere with the manufacture of new proteins, by destroying viral mRNA and inhibiting protein translation, not only in the
infected cell, but also in neighbouring uninfected cells.

Question 12

the most important factor in the defence against viral infections

Answer 12

the ability to shut down the metabolic activity of
normal cells in the body

Question 13

when a cell becomes infected by a virus, what does it produce

Answer 13

specialized
proteins called interferons

Question 14

the function of cytotoxic cells in the defence against viruses

Answer 14

kill their targets by releasing
granzymes and perforin from intracellular granules to
trigger programmed cell death (apoptosis) in
cancerous cells or those infected with bacteria or a
virus.

aka cell mediated defence

Question 15

describe the formation of T cells

Answer 15

they originate from hemapoetic stem cells, which differentiate into common progenitor cells

these then migrate into the thymus to mature, eventually forming the **thymocyte **

these then form the T cell, which undertakes cell mediated immune response

Question 16

describe the formation of B cells

Answer 16

originate from the hematopoetic stem cells , the differentiate into common progenitor cells in the bone marrow

these then form the developing B, whihc goes on to develop into the actual B cells

B cells primarily mature in the bone marrow, but they complete their maturation in secondary lymphoid organs like the spleen(upon encounter with antigens )

Question 17

the 2 major classes of T cell population

Answer 17

CD4(helper)
CD8(cytotoxic)

Question 18

CD4 function

Answer 18

synthesize and secrete signalling molecules with
activating or enhancing effects on most other cells involved in both the
adaptive and innate immune responses.

Question 19

HIV is a member of whihc group of viruses

Answer 19

retroviruses

Question 20

the HIV genome consists of two identical double-
stranded DNA molecules that are enclosed
within the core of the virus particle, true or false

Answer 20

false, it rather consists of two identical single-
stranded RNA molecules that are enclosed
within the core of the virus particle

Question 21

the enzyme that retroviruses(like HIV) contain and it’s function

Answer 21

reverse
transcriptase.

allows the virus to convert its RNA genome into DNA, which can then integrate into the host cell’s genome.

Question 22

the function of positive and negative factors in HIV replication cycle

Answer 22

Positive factors required for viral replication while negative factors suppress viral replication

Question 23

examples of positive factors in HIV replication cycle

Answer 23

CD4 Receptor
CCR5 Co-receptor
CXCR4 Co-receptor
Reverse Transcriptase
Integrase
NF-κB (Transcription Factor)
Host RNA Polymerase II

Question 24

examples of negative factors in HIV replication cycle

Answer 24

APOBEC3G
Tetherin
TRIM5α
Interferons
SAMHD1

Question 25

how many stages are there in HIV infection , name them

Answer 25

3

Acute retroviral syndrome
Chronic HIV Infection(asymptomatic or clinical latency period )
AIDS

Question 26

what happens in Acute retroviral syndrome stage of HIV

Answer 26

poses with symptoms similar to those of other diseases
usually lasts a week or two, then completely goes away

Question 27

what happens in the second stage of HIV(chronic HIV infection)

Answer 27

this stage has no symptoms, and can last for a period of 10 years.
During this period, CD4 T cells are attacked and destroyed by the untreated HIV infection, rendering the host more susceptible to other infections

note that a combination of medicines can help manage the HIV in this stage, rebuilding the immune system and prevneting spread of the infection.

Question 28

The normal count of CD4 T cells per microliter of blood

Answer 28

between 450 and 1,400 cells

Question 29

what happens during the third stage of HIV infection

Answer 29

CD4 T-cell number drops below 200. You can
also be diagnosed with AIDS if you have an “AIDS defining
illness” such as Kaposi’s sarcoma (a form of skin cancer) or
pneumocystis pneumonia (a lung disease).

Question 30

WHO stages of HIV infection

Answer 30

Primary HIV infection
Stage 1(asymptomatic)
Stage 2(mild disease )
Stage 3(moderate disease)
Stage 4(immunocompromise)

Question 31

HIV treatments

Answer 31

HIV fusion inhibitors (Enfuvirtide inhibits the fusion of HIV
to the host cells)

HIV integrase inhibitors (Dolutegravir)

HIV reverse transcriptase inhibitors (Doravirine, Efavirenz)

HIV protease inhibitors (Atazanavir)