Retroviruses Flashcards

1
Q

Describe the capsid of retroviruses

A

Helical nucleocapsid plus icosahedral or cylindrical outer capsid

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2
Q

What is the structure of the genome of retroviruses?

A

SS RNA

2 identical 35s RNAs joined by specific tRNAs; Diploid genome

Diploid genome

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3
Q

What is the enzymatic complex comprised of in retroviruses?

A

RNA dependent -DNA polymerase (reverse transcriptase)

DNA polymerase

RNAse H

Integrase

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4
Q

What part of the RNA genome do Chronic leukemia viruses lack?

A

ONC

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5
Q

What do Acute luekemia/Sarcoma viruses lack?

A

Usually lack env, but possess oncogenes

Exception is Rous Sarcoma - has everything

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6
Q

Where does replication of retroviruses take place?

A

Cytoplasm and Nucleus

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7
Q

Where does provirus formation take place?

A

Cytoplasm, then its transported to the nucleus

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8
Q

What are long terminal repeats?

A

Produced by the conversion of genomic RNA to proviral DNA

Located at each end of the provirus; has regulatory regions

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9
Q

What mRNAs are yielded from provirus transcription?

A

35s mRNA

28s mRNA

21sm mRNA

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10
Q

What product does 35s mRNA yield?

A

GAG or GAG-pol polyprotein

GAG mRNA predominates

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11
Q

What product does 28s mRNA yield?

A

Env polyprotein

Proteolytically cleaved into smaller proteins

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12
Q

What is the product of the 21s mRNA?

A

ONC protein

Present in acute leukemia/sarcoma virus

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13
Q

What is the difference between DNA tumor viruses and retroviruses?

A

DNA viruses - transform cells OR cause lytic infection

Retroviruses - transform cells AND produce progeny virus

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14
Q

How do chronic leukemia viruses cause leukemia?

A

Leukemia after long latent period;l activate protooncogenes that is already present in cell DNA

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15
Q

How do acute leukemia-sarcoma viruses cause disease?

A

SRC or other oncogene present, cause sarcoma in vivo

Usually defective for replication (except Rous sarcoma virus), require helper virus for replication

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16
Q

How does estrogen enhance tumor formation?

A

LTR has receptors for hormone

17
Q

What are four possible modes of protooncogene activation?

A

Chemical Carcinogen causes mutation in repressor gene

Insertion of leukemia virus near a protooncogene

Translocation of protooncogenes to another chromosome under influence of a promotor

Introduction of oncogene into cell by sarcoma or acute leukemia virus