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Medical Microbiology 1-15 > Lecture 9 > Flashcards

Lecture 9 Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

Some DNA and RNA viruses can transform normal cells into cancer cell. What are these viruses called?

A

Oncogenic viruses.

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2
Q

The cells that are capable of being transformed possess one or more types of these genes. Which are they?

A

The protooncogenes.

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3
Q

What is the name of the tumour producing RNA viruses?

A

Retroviruses

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4
Q

True of false. The ssDNA is used to form dsDNA

A

True

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5
Q

True or false. The ssRNA is transcribed into ssDNA by the enzyme RNa dependent DNA polymerase also called reverse transcriptase.

A

True

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6
Q

The dsDNA can enter the nucleus and become incorporated into what?

A

The host genome.

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7
Q

How are viruses released?

A

By budding from the membrane

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8
Q

How many mechanisms by which the retrovirus induce malignancies? Name the viruses.

A

Two. The Rous sarcoma virus (RSV) (infects chickens) and Avian leukosis virus (infects birds).

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9
Q

Define reverse transcriptase

A

An enzyme that catalyzes the formation of DNA from an RNA template in reverse transcription.

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10
Q

Name the four genes that are on the ssRNA of the Rous sarcoma virus. Where are they located?

A

gag codes= found in the capsid
pol codes for the reverse transcriptase
env codes for 2 glycoproteins
src codes for an enzyme that phosphorylate cellular proteins.

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11
Q

How many genes are on the ssRNA of the Avian leukosis?

A

3 genes

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12
Q

True or false. The Avian leukosis does not possess an oncogene, therefore, making it a non acute leukemia virus and it induces leukaemia after a latent period of time.

A

True.

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13
Q

How does the Avian leukosis virus become malignant?

A

Insertion of the DNA adjacent to a cell’s protooncogene. The insertion results

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14
Q

What are tumor-suppressor genes called?

A

Antioncogenes

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15
Q

What happens if these genes are altered or removed?

A

A mutation occurs.

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16
Q

True or false. Oncogenic DNA viruses dont exist.

A

False, they do exist.

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17
Q

What types of viruses have been strongly linked to human cancers?

A

Herpesviruses, papillomaviruses and hep B

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18
Q

How are do these viruses become malignant?

A

The gene product produces malignancies by ending with and inactivating timor-suppressor gene products.

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19
Q

When speaking of multiplication of animal viruses, the attachment and absorption is describe as what?

A

The cell contains specific receptors on its surface. Those receptors are recognized by attachment sites on the virus such as glycoprotein spikes.

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20
Q

During the penetration division- explain the envelope fusion.

A

The envelope contacts the cell membrane. There is a fusion of the two membranes and the nucleocapsid is released into the cytoplasm.

21
Q

Explain a similar process for naked viruses.

A

The virus is engulfed by the cell like phagocytosis and the nucleocapsid is released into the cytoplasm.

22
Q

Explain the uncoating process.

A

It’s the removal of the capsid by the activity of certain enzymes. This exposes the viral nucleic acid. This occurs in the nucleus for the herpesviruses.

23
Q

True or false. The viral nucleic acid is replicated so that the numerous copies are produces during the replication process.

A

True

24
Q

Explain how the capsid proteins are of use during the replication process.

A

The viral nucleic acid through the mRNA, directs the synthesis of certain proteins. Some of these are the capsid proteins.

25
Q

Where does most of the assembly take place in the viruses.

A

This process takes place in the cytoplasm for most viruses and in the nucleus for some.

26
Q

Explain the process of assembly.

A

Copies of the nucleic acid associated with incomplete capsids and nucleocapsids are formed.

27
Q

True or false. Viruses are the tiniest microorganism.

A

True

28
Q

Explain what the following statement means. Viruses are obligate intracellular parasites.

A

Viruses can only grow inside the cell of an organism.

29
Q

True or false. Viruses are structurally complexe.

A

False. Viruses are structurally simple.

30
Q

What consists of a virion? Name the three. Define virion.

A

A virion is a complete virus- which means that is consists of a genetic material such as DNA or RNA, the protein coat called the capsid and a membranous envelope.

31
Q

What is a capsid?

A

A protein coat

32
Q

True or false. The membranous envelope found is found in all viruses?

A

False. They are found in some viruses but not all.

33
Q

Explain the replication process of the virus cell.

A

A virus cell will not grow then divide. Rather, they multiply inside the cell by making copies of their individual parts and then assembling them.

34
Q

True or false. The invasion of a single virus cell can result in the formation of hundred of viruses and can infect other cells.

A

True.

35
Q

Name the three types of viruses cells.

A

Animal viruses
Plant viruses
Bacterial viruses

36
Q

Give a synonym for bacterial viruses.

A

Bacteriophages or phages.

37
Q

Define viroids

A

are the smallest infectious pathogens known. They are solely composed of a short strand of circular, single-stranded RNA without protein coat.

38
Q

Define prions

A

Prions, so-called because they are proteinaceous, are infectious particles, smaller than viruses, that contain no nucleic acids (neither DNA nor RNA).

39
Q

Define a icosahedral virus.

A

This type of virus has a icosahedral capsid surrounding the nucleic acid core. It has 20 triangular faces and 12 corners.

40
Q

Describe the helical virus

A

They are rod shaped as the nucleic acid core is surrounded by a cylindrical capsid in the form of a helix.

41
Q

True or false. The icosahedral viruses and the helical viruses can’t be enveloped. Elaborate.

A

False. They both can be enveloped as the nucleocapsid is surrounded by a lipid membrane.

42
Q

True or false. The helical viruses have their nucleocapsids folded within the envelope due to the viruse’s spherical shape.

A

True

43
Q

True or False. A virus can have a DNA or RNA which can be a single strand (ss) or double stand (ds).

A

True

44
Q

Explain where the proteins are bound by in helical virions.

A

End to end to forma ribbon

45
Q

Explain what the capsomers consists of for the icosahedral virions.

A

They consist of a number of proteins.

46
Q

Define what envelopes are.

A

They are the bacterial cell membrane. They are a lipid bilayer with an interspersed protein.

47
Q

Name the two types of proteins when referring to envelopes.

A

Glycoproteins and matrix proteins.

48
Q

What do glycoproteins resemble under the electron microscopy.

A

Like spikes on the surface of the virion.

49
Q

True or false. Disinfectants can dissolve the envelope, such as a esther.

A

False. Disinfectants can dissolve the envelope such as an ether.

Medical Microbiology 1-15 (15 decks)

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