Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL 3155 > Chapter 28 > Flashcards

Chapter 28 Flashcards

Retroviruses

1
Q

Rous showed

A

Rous Sarcoma virus inducing tumor formation in chickens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Retroviridae has 7 genera, grouped based on

A

differences in morphology, genome organization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

there is Lentivirus of

A

HIV type 1 with humans as host

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

general virion structure

A

enveloped, icosahedral or conical capsids with 3 different enzymes contained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

the three different enzymes are

A

reverse transcriptase, integrase, protease; encoded by viral genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

the virion contains inside

A

tRNA, 2 copies of RNA genome (diploid and dimerized)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

on the surface it has

A

transmembrane protein, surface protein (bound to TM), matrix protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

on the capsid it has

A

capsid protein (icosahedral) and nucleocapsid protein (coating genome)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

inside the lipid bilayer, there is

A

matrix protein and capsid protein, cpsid protein and nucleocapsid proatein coating the genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

general genome structure

A

(+)-sensed ssRNA, 5’-capped and 3’-poly(A)
repeated sequence of R at 5’ and 3’ ends
unique regions of U5 and U3
primer binding sequence and polypurine tract
splice sites 5’SS and 3’SS
[psi] is at downstream of 5’SS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

U5 contains

A

RNA dimerization hairpin that allows RNA to interact, where both RNAs interact with each other through U5 sequence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

PBS binds to

A

tRNA in the virion. the type of tRNA packaged into genome is dependent on the virus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

SS is used to

A

splice out that part of genome and generate spliced mRNA.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

[psi] is a packaging signal that

A

used to create an assembly of progeny virus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

polypurine tract is important for

A

transcription reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

there are three main polyproteins genes

A

group-specific antigen
polymerase (readthrough/framshift)
envelope (spliced mRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

surface protein (SU) recognizes

A

specific cell receptors, which indicates what type of cells the virus infect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

after binding, the virus either

A

fuses with plasma membrane (endocytosis)

or pH-dependent fusion mediated by TM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

once the penetration happens, capsid (CORE) is inside the cell, and

A

reverse transcriptase will start to copy RNA and synthesize dsDNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

after reverse transcription, dsDNA and proteins can be either

A

directly transported into nucleus as Lentiviruses and HIV, or must wait until nuclear envelope to desintegrate during the cell cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

integration occurs to

A

the host’s genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

for synthesizing complementary DNA, both

A

RNA and DNA can be used as a template

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

RT starts as

A

tRNA inside the virion binds to PBS in the viral genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

RT needs

A

vRdDP and rDdDp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

once tRNA bound, enzyme uses this as

A

a primer to initiate synthesis of (-)-sensed DNA (Strong-stop DNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

When the synthesis reaches the end of the genome,

A

it ends abruptly.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

after the stop of synthesis,

A

RNAse H (Ribonuclease H) digestion occurs to get a complement of U5’ and R5’ regions of newly synthesized DNA to be exposed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

R is also present at 3’ end, and the newly synthesized DNA is transferred to

A

R at the 3’ end, to continue with the synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

after the continuation of DNA synthesis from the 3’ end to PBS,

A

another RNAase H digestion occurs, with ppt remaining intact to the DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

another synthesis occurs on ppt with

A

(+)-strand strong-stop DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

once (+)-strand strong-stop DNA is made,

A

RNAse H digestion occurs with second strand of U3-R-U5-PBS to PBS’ of the first synthesized genome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

when two DNA genomes are hybridized,

A

extension of both DNA strands occur with forming LTR.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

LTR is

A

a long terminal repeats on proviral DNA genome with U3, R, U5 sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

RT is

A

RdDp and DdDp that is primer dependent for synthesis initiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

the order of RT is

A

(+)-stranded ssRNA -> (-)-stranded DNA -> dsDNA in CORE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

RT has no

A

3’-to-5’ exonuclease, consequently no proofreading

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

due to 1-10 substitutions per genome, the virus is considered

A

quasipecies that has variants in a single infeciton that differ by a small number of mutations

38
Q

quasispecies are allowed for

A

rapid adapation, facilitating drug resistance

39
Q

proviral integration happens at

A

random sites within the cellular genome

40
Q

integration is catalyzed by

A

the viral integrase (IN)

41
Q

to initiate, integrase binds to

A

both ends of dS DNA and brings them close to cDNA

42
Q

near the cDNA, integrase

A

removes 2 nucleotids from each 3’ end of the dsDNA, makes 4-6 nucleotides cut in cDNA, and ligate 3’ ends of vDNA to cDNA

43
Q

the ligation results mismatches of gaps that allow

A

host’s enzymes to repair two unpaired viral nucleotides that stick out

44
Q

provirus becomes part of host cell chromosome is replicated

A

along with host genome

45
Q

proviral integration makes spread of infection by

A

infection of new cells with progeny virus,

multiplication of cells with integrated proviral DNA

46
Q

integrated proviral DNA in egg or sperm can

A

transmit virus to offspring

47
Q

integration makes the virus difficult to

A

be cured, because it is latent and does not express

48
Q

after the RT and integration,

A

expression of viral RNA, viral protein synthesis, virion assembly are followed

49
Q

in the genome replication, there are enhancer sequences and TATA in U3 sequence that recruit

A

TFs to U3 regiong, bringing cellular polymerase

50
Q

when Pol II is brought to the LTR [L], it will begin

A

transcription initiation, with Pol III transcribing R sequence through U5 and to LTR [R]

51
Q

in LTR [R], AAUAAA signal is for

A

cleavage and polyadenylation, with CF coming to cleave RNA after R sequence

52
Q

transcribed RNA has

A

5’cap and poly[A] tails

53
Q

full-length RNA transcribed can be for

A

mRNA or genome

54
Q

translation of the RNA can be made for

A

Gag or Gag/Pol

55
Q

transcribed RNA can be spliced to

A

remove Gag/Pol sites with 5’ss and 3’ss

56
Q

the spliced mRNA can be used for

A

translating the Env gene

57
Q

[psi] is the packaging signal only present in

A

full RNA, not present in spliced RNA

58
Q

the LTR [L] is used for intiation, because

A

complex binding to it will dislodge the LTR

59
Q

during transcription of proviral DNA, Promoter Occlusion TFs and RNA Pol complex that bind to the LTR [L] would

A

remove any complex bound to the LTR [R]. defining directionality

60
Q

Only LTR [R] that gets transcribed is

A

U3, because it has signal function of directing poly[A] and cleavage with AAUAAA signal

61
Q

U3 on LTR [L] is not

A

transcribed

62
Q

the AAUAAA located in U3 allows the CF to find

A

cleavage signal in the R region, in which one from LTR [R] will enhance R to be recognized

63
Q

however, AAUAAA is actually located in R, but it is U3 that contains

A

enhancer of AAUAAA that functions in RNA only

64
Q

simple retroviruses make

A

full lengthed and spliced mRNAs

65
Q

full length mRNA is used for

A

expression of Gag polyproteins that process into MA, NC, CA

66
Q

ribosomes can also make

A

Gag/Pol to make PR, RT and INT as well, made in smaller amounts

67
Q

synthesis of Pol is regulated to be less than

A

synthesis of Gag

68
Q

for gamma, Gag/Pol is made by

A

readthrough at stop codon after Gag reading frame UAG->CAG (glu)

69
Q

for HIV, Gag/Pol is done by

A

frameshift, moving one nucleotide backward to resume in translation

70
Q

after spliced, mRNA with Env gene can generate

A

SU and TM proteins

71
Q

normally, the ribosome in retrovirus stops translating Gag gene at

A

AAA/AAC, upstream of a hairpin

72
Q

when stopped at the AAA/AAC, the ribosome occassionally moves one nucleotide backward to be in a frame of

A

AAA/AAA, not recognizing the stop codon

73
Q

AAA/AAC and AAA/AAA can be possible, because both interact with

A

RNA codon and tRNA codons (Phe and Leu) are very similar

74
Q

NC binds to

A

[Psi] which will nucleate assembly

75
Q

SU and TM process from Env are translated in

A

ER and go through the Golgi and transported to PM

76
Q

after nucleate assembly,

A

CA is added next to form a core

77
Q

newly formed core buds from cytosol into

A

plasma membrane, along with SU and TM

78
Q

PR mediates

A

maturation

79
Q

two classes of oncogenic retrovirsues are

A

acute transforming and nontransforming

80
Q

acute transforming is when

A

rapidly transformed cultured cells and induce cancer quickly

81
Q

nontransforming is when

A

inducing cancer after a long latency period

82
Q

acute transforming retroviruses encode

A

extra protein not required for virus replication

83
Q

Rous contains

A

src, sarcoma

84
Q

src is almost identical to a cellular gene of

A

c-src (tyrosine kinase) that regulates cell cycle

85
Q

nontransforming retrovirus does not encode

A

an oncogen

86
Q

nontransforming retrovirus results

A

loss of regulation from integration in or near cellular genes that alter normal expression fo cellular gene

87
Q

when a promoter insertion happens with exon 1 in upstream of the viral genome,

A

the transcription from LTR [R] occurs without a proper amount or timing

88
Q

a potential of gene-therapy can be found from

A

the retrovirus ability to integrate into host genome to “replace defective genes”

89
Q

retroviral vectors often made with

A

Gag, Pol and Env deleted to prevent virus replication, and desired genes to take the place of viral genes

90
Q

the limitation of the retrovirus-based gene-therapy is

A

size limit on RNA that can be packaged, and insertion of gene near oncogene can cause cancer

91
Q

retroviral gene therapy has been used for treatment of

A

SCID, from a mutation in a cellular receptor required for differentiation of T-lymphocytes

92
Q

SCID is treated with

A

removing hematopoietic stem cells, infect cells with retroviral vector containing normal gene, reintroduce cells into body to differentiate and proliferate

BIOL 3155 (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions