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MCP Unit 1 > Lecture 4: Nuclear Structure And Function > Flashcards

Lecture 4: Nuclear Structure And Function Flashcards

0
Q

How is the nuclear envelope characterized?

A

Double membrane

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1
Q

what are the 4 functions of the nuclear pore?

A
  1. Protect xs from damaging agents in cytosol
  2. Repair damages xs
  3. Transcription
  4. Construct ribosomes
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2
Q

Is the nucleolus surrounded by a membrane?

A

No

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3
Q

Which two structures/features have ribosomes?

A

Outer nuclear membrane

ER

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4
Q

What are Lamins A B and C and what purpose do they serve?

A

Intermediate filament proteins of the nuclear lamina

Support nuclear envelope, organize xs, regulate nuclear breakdown at mitosis

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5
Q

Do all proteins need a nuclear localization or nuclear export signal to pass through NPCs?

A

No. Proteins smaller than 44kDa (and small solutes$ can passively diffuse

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6
Q

Where is Ran GAP located and what does it do?

A

Cytoplasmic side

GTP hydrolysis to dissociate ran from complex BEFORE IMPORT or entire complex AFTER EXPORT

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7
Q

Where is Ran GEF located and what does it do?

A

Nuclear side

Allows Ran to attach to importin AFTER IMPORT or BEFORE EXPORT

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8
Q

What does an importin do?

A

Recognizes and binds nuclear localization signal. Docks on NPC. Accompanies cargo.

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9
Q

What does an exportin do?

A

RNA export.

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10
Q

What is the function of the nucleolus?

A

Ribosome biogenesis

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11
Q

Where is the fibrillar center and what does it do?

A

Nucleolus

DNA not actively transcribed

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12
Q

Where is the dense fibrillar component and what does it do?

A

Nucleolus

Where rRNA molecules are synthesized

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13
Q

Where is the A Granular Component and what does it do?

A

Maturing ribosomal precursor particles

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14
Q

Which ribosomal subunit is made first?

A

Small (18S)

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15
Q

Where is satellite DNA found, and how is it characterized,

A

Telomeres and centromeres

Repeated sequences

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16
Q

What are the three prominent sequence elements needed to stabilize and duplicate chromosomes,

A

Replication origin
Telomeres
Centromeres

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17
Q

What are alu sequences?

A

Repetitive DNA

Contain recognition sequence for restriction enzyme Alu

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18
Q

What do alu sequences, transposons, and pseudogenes have in common?

A

Repetitive DNA

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19
Q

How do pseudogenes arise?

A

Duplication, became non-functional through genetic drift

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20
Q

What comprises chromatin?

A

Chromosomal DNA, histones, and regulatory proteins

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21
Q

How many base pairs are wrapped around each histone core?

A

146bp

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22
Q

How many base pairs per nucleosome?

A

~200bp

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23
Q

What is the site for post-translational modifications in histones, and what kinds of modifications are made?

A

Histone tail

Acetylation, methylation (Lys), phosphorylation (Ser)

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24
Q

What is the nuclear matrix comprised of, and what is it for?

A

Proteins
Structure and organization for nucleus
Xs attach

25
Q

Where do xs attach to the nuclear matrix?

A

Matrix-associated regions (MARs)

26
Q

Human cells undergo open mitosis. What does this mean?

A

Nucleus is completely disassembled

27
Q

Phosphorylation and dephosphorylation of which proteins causes the nuclear envelope to break down before mitosis, and to reassemble after mitosis?

A

Almond

28
Q

Which disease is autoimmune, characterized by antibodies to self-antigens in the nucleus?

A

Systemic lupus erythematosus

29
Q

Which disease is a cancer of promyelocytes, caused by a mutation in in PML nuclear protein, needed to make a nuclear compartment?

A

Acute promelocytic leukemia

30
Q

Which disease is caused my mutations in the protein SMN (survival of motor neurons) involved in RNA splicing?

A

Spinal muscular atrophy

31
Q

what are the RNA components of the large ribosomal subunit and where are they synthesized?

A

28S rRNA - nucleolus
5.8S rRNA - nucleolus
5S rRNA - elsewhere in nucleus

32
Q

What is the RNA component of the small ribosomal subunit, and where is it synthesized?

A

18S - nucleolus

33
Q

What would be the result if Ran-GEF had a loss of function mutation?

A

Nuclear side
GDP –> GTP on Ran
Needed for export
Export would stop

34
Q

What percent of spontaneous miscarriages are due to chromosomal abnormalities?

A

60%

35
Q

What percent of recognized pregnancies end in spontaneous abortion, and what percent of miscarriages happen in the first trimester?

A

15% miscarriages

80% first trimester

36
Q

Of miscarriages due to chromosomal abnormalities, what percent have autosomal trisomies?

A

52%

37
Q

What proportion of conceptuses have chromosomal abnormality? What proportion of these are live born?

A

1 in 13 have xs abnormality

6/1000 are live born

38
Q

What percent of newborns have a chromosomal anomaly?

A

0.6%

39
Q

What are the specimen used for karyotype analysis?

A

Blood (must have nucleus), amniotic fluid, chorionic villi, bone marrow, tissue

40
Q

In what phase are cells arrested for karyotype analysis?

A

Metaphase

41
Q

What is TTAGGG

A

Common repeat sequence of telomere

42
Q

What are the short and long arms of chromosomes called?

A

P and Q arms

43
Q

How is the banding pattern on chromosomes visualized?

A

Giemsa or Wright’s stain
+ dyes
Mild trypsinization weakens DNA-protein interactions, giving banding pattern

44
Q

Is chromosome polymorphous an abnormality or normal variation?

A

Normal variation

45
Q

What is chromosome polymorphism?

A

Natural in population

Two or more alternative structural forms for a chromosome in a population

46
Q

How is euploidy different from aneuoloidy?

A

Euploidy - multiples of one complete xs complement (N 2N 3N 4N)
Aneuoloidy - gain or loss of xs equalling less than one complete compliment (mobosomy, trisomy)

47
Q

How are aneuoloidies normally acquired?

A

Not inherited

Meiotic or mitotic nondisjunction

48
Q

Are aneuoloidies usually compatible with life?

A

No

49
Q

What is mosaicism and can it be inherited?

A

Presence of at least 2 different cell lines with at least one clear variation between them
Cannot be inherited

50
Q

What are the three viable autosomal trisomies?

A

Down syndrome: trisomy 21
Patau syndrome: trisomy 13
Edwards syndrome: trisomy 18

51
Q

Failure to thrive, cleft lip and palate, rocker bottom feet, polydaxtyly, punched out scalp, small head, heart defect

A

Patau syndrome

52
Q

Which trisomy has an incidence of 1/700 live births?

A

Down syndrome trisomy 21

53
Q

Low birth weight, small mouth and jaw, ventricular septal defect, hypoplasia of muscles, prominent occiput, low-set malformed ears, rocker bottom feet, crossed fingers

A

Edwards syndrome

Trisomy 18

54
Q

Why are sex chromosome anomalies usually milder than autosome anomalies?

A

X inactivation

Limited number of genes on Y

55
Q

How do sex chromosome anomalies occur?

A

Nondisjunction errors in meiosis

56
Q

What is the region on the short arms of the sex chromosomes that engages in recombination?

A

Pseudoautosomal region

57
Q

Why are sex chromosome anomalies usually milder than are autosome anomolies?

A

X inactivation

Limited number of genes on Y

58
Q

How do sex chromosome anomalies occur?

A

Nondisjunction errors in meiosis

59
Q

What is the region on the short arm of the sex chromosomes that engages in recombination?

A

Pseudoautosomal region

MCP Unit 1 (7 decks)

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