Molec Cell > the nucleus > Flashcards

the nucleus Flashcards

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1
Q
  1. the principal difference between eukaryotic and prokaryotic cells is that eukaryotic cells have
    a. larger ribosomes than prokaryotic cells
    b. cell walls, while prokaryotic cells do not
    c. DNA replication and transcription in the same compartment, while prokaryotic cells do not
    d. A nucleus, while prokaryotic cells do not
A

d. A nucleus, while prokaryotic cells do not

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2
Q
  1. By restricting the traffic of proteins and RNA across the nuclear envelope, eukaryotic cells can regulate
    a. Translation
    b. Transcription
    c. Endocytosis
    d. Nuclear pH
A

b. Transcription

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3
Q
  1. The major pathway for molecules to pass into and out of the nucleus is through
    a. Gap junctions between the nuclear envelope membranes
    b. Porin channels in the nuclear envelope membranes
    c. Nuclear pore complexes
    d. Diffusion through the membrane bilayers of the nuclear envelope
A

b. Porin channels in the nuclear envelope membranes

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4
Q
  1. The nuclear envelope is continuous with the
    a. Mitochondrial outer membrane
    b. Rough endoplasmic reticulum
    c. Golgi apparatus
    d. Plasma membrane
A

b. Rough endoplasmic reticulum

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5
Q
  1. The nuclear lamina is built of proteins called
    a. Lamins
    b. Laminins
    c. Nucleins
    d. Nucleoplasmins
A

a. Lamins

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6
Q
  1. The filaments of the nuclear lamina are composed of a type of
    a. Microfilament
    b. Microtubule
    c. Intermediate filament
    d. Thick filament
A

c. Intermediate filament

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7
Q
  1. The nuclear lamina binds to
    a. Both the inner nuclear envelope membrane and the chromatin
    b. The inner nuclear envelope only
    c. The chromatin only
    d. Neither the inner nuclear envelope nor the chromatin
A

a. Both the inner nuclear envelope membrane and the chromatin

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8
Q
  1. The associations of lamins with the inner nuclear envelope membrane is via
    a. Lamin binding to proteins in the nuclear envelope membrane
    b. GPI anchors on lamins
    c. Lipid tails on lamins
    d. Both a and c
A

a. Lamin binding to proteins in the nuclear envelope membrane

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9
Q
  1. Which of the following is a nuclear lamina disease
    a. Emery-Dreifuss muscular dystrophy
    b. Charcot-Marie-Tooth disorder type 2B1
    c. Hutchinson-Gilford progeria syndrome
    d. All of the above
A

c. Hutchinson-Gilford progeria syndrome

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10
Q
  1. Nuclear pores are organized with ___ symmetry
    a. Sixfold
    b. Eightfold
    c. Ninefold
    d. Tenfold
A

b. Eightfold

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11
Q
  1. Small molecules (molecules<20 kd) enter nuclei by way of
    a. Passive diffusion through nuclear pore complexes
    b. Selective transport through nuclear pore complexes
    c. Active transport across the nuclear envelope membranes
    d. Passive diffusion across the nuclear envelope membranes
A

d. Passive diffusion across the nuclear envelope membranes

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12
Q
  1. Export of RNAs from the nucleus occurs primarily by
    a. Passive diffusion through nuclear pore complexes
    b. Cotranscriptional insertion through nuclear envelope membrane protein pores
    c. Selective transport through nuclear pore complexes in association with proteins
    d. Release from the nucleus when it breaks down at mitosis
A

c. Selective transport through nuclear pore complexes in association with proteins

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13
Q
  1. The nuclear localization signal is recognized by and binds to which protein in the process of nuclear protein import
    a. Ran
    b. Importin
    c. Exportin
    d. The outer fibril protein
A

b. Importin

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14
Q
  1. Nuclear localization signals were first identified by Alan Smith and his colleagues in the protein
    a. Nucleoplasmin
    b. Histone H1
    c. Lamin B
    d. SV40 T antigen
A

d. SV40 T antigen

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15
Q
  1. The nuclear localization signal is typically a(n) ___, rich in the amino acids ___
    a. -helix; Pro, Lys, and Arg
    b. -helix; Leu, Phe, and Gly
    c. short chain; Lys and Arg
    d. short chain; Phy and Gly
A

c. short chain; Lys and Arg

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16
Q
  1. what localization occurs for proteins that are normally nuclear when their nuclear localization signal is deleted and the protein is injected into the cytoplasm of cultured cells
    a. nucleus
    b. cytoplasm
    c. in a ring around the outside of the nuclear envelope
    d. extracellular
A

c. in a ring around the outside of the nuclear envelope

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17
Q
  1. transport of RNAs out of the nucleus involves all but which of the following
    a. Ran
    b. Expenditure of chemical energy
    c. Protein translocation signals
    d. Small RNAs crossing by passive diffusion
A

d. Small RNAs crossing by passive diffusion

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18
Q
  1. snRNAs are synthesized in the
    a. nucleus and function in the cytoplasm
    b. cytoplasm and function in the nucleus
    c. nucleus and function in the nucleus without passing into the cytoplasm
    d. nucleus, move to the cytoplasm to pick up proteins to become functional, and then return to the nucleus
A

d. nucleus, move to the cytoplasm to pick up proteins to become functional, and then return to the nucleus

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19
Q
  1. the directionality of nuclear transport is determined by ___ in the nucleus and ___ in the cytosol
    a. high Ran; low Ran
    b. low Ran; high Ran
    c. high Ran/GTP; high Ran/GDP
    d. high Ran/GDP; high Ran/GTP
A

c. high Ran/GTP; high Ran/GDP

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20
Q
  1. Highly condensed, transcriptionally inactive chromatin is called
    a. Euchromatin
    b. Heterochromatin
    c. A chromatin domain
    d. Histone-containing chromatin
A

b. Heterochromatin

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21
Q
  1. Facultative heterochromatin is heterochromatin that contains
    a. Sequences inactive in one cell type but active in others
    b. DNA sequences that are not transcribed in any cell type
    c. A mixture of heterochromatin and euchromatin
    d. Heterochromatin that functions in ways other than for transcription
A

a. Sequences inactive in one cell type but active in others

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22
Q
  1. Ciliated protozoa have a transcriptionally
    a. Active nucleus that participates in sexual reproduction
    b. Inactive nucleus that participates in sexual reproduction
    c. Inactive nucleus that participates in sexual reproduction and a transcriptionally active nucleus that does not participate in sexual reproduction
    d. Active nucleus that participates in sexual reproduction and a transcriptionally inactive nucleus that does not participate in sexual reproduction
A

c. Inactive nucleus that participates in sexual reproduction and a transcriptionally active nucleus that does not participate in sexual reproduction

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23
Q
  1. Chromatin that contains sequences that are not transcribed in any cell type is called
    a. Constitutive heterochromatin
    b. Facultative heterochromatin
    c. Constitutive euchromatin
    d. Facultative euchromatin
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A

a. Constitutive heterochromatin

24
Q
  1. Chromosomes are attached to the nuclear envelope by
    a. Centromeres
    b. Telomeres
    c. Origins of replication
    d. Nuclear lamin genes
    e. Both a and b
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A

d. Nuclear lamin genes

25
25. Chromatin domains are loops of about ___ base pairs of DNA a. 1000 b. 10,000 c. 100,000 d. 1,000,000
b. 10,000
26
26. functional domain loops can be seen by viewing ___ chromosomes with light microscopy a. normal interphase b. lampbrush c. metaphase d. anaphase
b. lampbrush
27
27. sites of newly replicated DNA can be detected with antibodies if the DNA is labeled with a. tritiated thymidine b. tritiated uridine c. bromodeoxyuridine d. bromodeoxythymidine
d. bromodeoxythymidine
28
28. newly replicated DNA is located in a few hundred spots in the nucleus because there are a. a few hundred origins of replication per nucleus b. a few thousand origins of replication but only a few hundred are active at any one time c. a few thousand origins of replication active at any one time, but they are located in a few hundred discrete clusters d. none of the above
c. a few thousand origins of replication active at any one time, but they are located in a few hundred discrete clusters
29
29. cajal bodies are sites of a. RNA transcription b. RNA processing c. Ribosome assembly d. DNA replication
c. Ribosome assembly
30
30. The nucleolus is the site where ___ is/are assembled a. Nuclear pores b. Ribosomal subunits c. Chromatin d. The nuclear matrix
b. Ribosomal subunits
31
31. The eukaryotic 45S pre-rRNA transcript codes for the a. 28S rRNA b. 28S and 18S rRNAs c. 28S, 18S, and 5.8S rRNAs d. 28S, 18S, 5.8S, and 5S rRNAs
c. 28S, 18S, and 5.8S rRNAs
32
32. the region of chromosomes that codes for most of the rRNAs is called the a. nucleolus b. nucleolar organizing region c. ribosomal assembly region d. ribosomal organizer region
b. nucleolar organizing region
33
33. when spread out and viewed with electron microscopy, an active rRNA gene looks like a a. star of david b. Christmas tree c. Reindeer d. Santa claus
b. Christmas tree
34
34. Ribosomes leave the nucleus as a. Intact 80S ribosomes b. Intact 70S ribosomes c. 40S and 60S ribosomal subunits d. 18S and 28S rRNAs
c. 40S and 60S ribosomal subunits
35
35. splicing of pre-rRNA produces a. the 28S rRNA b. the 18S rRNA c. both 28S and 18S rRNAs d. none of the above
d. none of the above
36
36. most snoRNAs function in a. cleaving the 45S rRNA b. splicing cleaved rRNAs c. splicing cleaved mRNAs d. guiding regions of rRNAs to modifying enzymes
c. splicing cleaved mRNAs
37
37. Which of the following does not take place in the nucleus a. DNA replication b. Translation c. RNA processing d. Transcription
b. Translation
38
38. The outer nuclear membrane is contiguous with a. The endoplasmic reticulum b. The nuclear lamina c. The golgi apparatus d. The plasma membrane
a. The endoplasmic reticulum
39
39. The fibrous proteins underlying the inner nuclear membrane are a. Band 3s b. Collagens c. Keratins d. Lamins
d. Lamins
40
40. One working hypothesis for explaining the phenotypic consequences of nuclear lamina diseases is termed “gene expression”. The other is called a. “ablative shearing” b. “degradative acceleration” c. “mechanical stress” d. “targeting insufficiency”
a. “ablative shearing”
41
41. the nuclear pore complex of proteins is estimated to have a mass a. smaller than that of a ribosome b. about the same as that of a ribosome c. about five times that of a ribosome d. about 30 times that of a ribosome
d. about 30 times that of a ribosome
42
42. the nuclear basket protein complex is a component of the nuclear pore complex found a. inside the nucleus b. buried in the nuclear envelope c. on the cytoplasmic face of the pore d. lining the central channel of the pore
a. inside the nucleus
43
43. “Classical” nuclear localization signals are composed primarily of a. hydrophobic amino acids b. acidic amino acids c. basic amino acids d. sulfur-containing amino acids
c. basic amino acids
44
44. what is the function of karyopherins a. they attach to chromosomes in order to activate heterochromatin b. they coat chromosomes c. they define the structure of Cajal bodies d. they transport macromolecules into or out of the nucleus
d. they transport macromolecules into or out of the nucleus
45
45. the directionality of nuclear protein import is determined by a. a Ran/GTP gradient b. importin c. an ion gradient d. the nuclear lamina
a. a Ran/GTP gradient
46
46. the location of Ran GAP in association with the cytoplasmic filaments of the nuclear pore results in the conversion of the nucleotide bound to Ran in the cytoplasm. This nucleotide is a. ADP b. GDP c. ATP d. GTP
b. GDP
47
47. The import of the transcription factor NFKB into the nucleus is regulated by a. A nuclease b. A protease c. A phospholipase d. A protein kinase
d. A protein kinase
48
48. mRNA molecules are exported from the nucleus to the cytoplasm via a. a consensus sequence located at the 3’ terminus b. the 7-methylguanosine cap structure c. importin d. associated proteins that contain export signals
d. associated proteins that contain export signals
49
49. functional snRNPs are assembled in the a. cytoplasm b. nucleolus c. nucleoplasm d. PML body
a. cytoplasm
50
50. Which of the following is not true of heterochromatin a. It is highly condensed chromatin b. There are two forms of it, called constitutive and facultative heterochromatin c. It is transcriptionally active d. It is largely localized to the nuclear periphery
c. It is transcriptionally active
51
51. Chromosomes are distributed in the nucleus a. As cleavage fragments b. As condensed mitotic chromosomes c. Randomly d. In distinct territories
d. In distinct territories
52
52. What is the average number of replication forks per DNA replication cluster in a mammalian cell nucleus a. 8000 b. 4000 c. 200 d. 40
d. 40
53
53. which of the following are not sub-compartments of the nucleus a. clustered DNA replication sites b. liquid droplets c. PML bodies d. Speckles enriched in RNA splicing components
b. liquid droplets
54
54. The nucleolus is the site where a. Ribosomal RNA is transcribed and ribosomes are assembled b. DNA replication occurs c. Proteins recently imported from the cytoplasm are deposited d. Translation occurs
a. Ribosomal RNA is transcribed and ribosomes are assembled
55
55. Which of the following is a possible intermediate during pre-rRNA processing a. An RNA molecule containing 18S + 5.8S rRNAs b. An RNA molecule containing 5.8S + 28S rRNAs c. An RNA molecule containing 5S + 28S rRNAs d. An RNA molecule containing 18S + 28S rRNAs
a. An RNA molecule containing 18S + 5.8S rRNAs
56
56. Most snoRNAs function as a. Catalytic RNAs b. Guide RNAs c. Self-replicating RNAs d. Self-splicing RNAs
b. Guide RNAs
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