Lecture 4: Nuclear Structure And Function

Question 0

How is the nuclear envelope characterized?

Answer 0

Double membrane

Question 1

what are the 4 functions of the nuclear pore?

Answer 1

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

Question 2

Is the nucleolus surrounded by a membrane?

Answer 2

No

Question 3

Which two structures/features have ribosomes?

Answer 3

Outer nuclear membrane

ER

Question 4

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

Answer 4

Intermediate filament proteins of the nuclear lamina

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

Question 5

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

Answer 5

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

Question 6

Where is Ran GAP located and what does it do?

Answer 6

Cytoplasmic side

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

Question 7

Where is Ran GEF located and what does it do?

Answer 7

Nuclear side

Allows Ran to attach to importin AFTER IMPORT or BEFORE EXPORT

Question 8

What does an importin do?

Answer 8

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

Question 9

What does an exportin do?

Answer 9

RNA export.

Question 10

What is the function of the nucleolus?

Answer 10

Ribosome biogenesis

Question 11

Where is the fibrillar center and what does it do?

Answer 11

Nucleolus

DNA not actively transcribed

Question 12

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

Answer 12

Nucleolus

Where rRNA molecules are synthesized

Question 13

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

Answer 13

Maturing ribosomal precursor particles

Question 14

Which ribosomal subunit is made first?

Answer 14

Small (18S)

Question 15

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

Answer 15

Telomeres and centromeres

Repeated sequences

Question 16

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

Answer 16

Replication origin
Telomeres
Centromeres

Question 17

What are alu sequences?

Answer 17

Repetitive DNA

Contain recognition sequence for restriction enzyme Alu

Question 18

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

Answer 18

Repetitive DNA

Question 19

How do pseudogenes arise?

Answer 19

Duplication, became non-functional through genetic drift

Question 20

What comprises chromatin?

Answer 20

Chromosomal DNA, histones, and regulatory proteins

Question 21

How many base pairs are wrapped around each histone core?

Answer 21

146bp

Question 22

How many base pairs per nucleosome?

Answer 22

~200bp

Question 23

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

Answer 23

Histone tail

Acetylation, methylation (Lys), phosphorylation (Ser)

Question 24

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

Answer 24

Proteins Structure and organization for nucleus Xs attach

Question 25

Where do xs attach to the nuclear matrix?

Answer 25

Matrix-associated regions (MARs)

Question 26

Human cells undergo open mitosis. What does this mean?

Answer 26

Nucleus is completely disassembled

Question 27

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

Answer 27

Almond

Question 28

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

Answer 28

Systemic lupus erythematosus

Question 29

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

Answer 29

Acute promelocytic leukemia

Question 30

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

Answer 30

Spinal muscular atrophy

Question 31

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

Answer 31

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

Question 32

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

Answer 32

18S - nucleolus

Question 33

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

Answer 33

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

Question 34

What percent of spontaneous miscarriages are due to chromosomal abnormalities?

Answer 34

60%

Question 35

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

Answer 35

15% miscarriages | 80% first trimester

Question 36

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

Answer 36

52%

Question 37

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

Answer 37

1 in 13 have xs abnormality | 6/1000 are live born

Question 38

What percent of newborns have a chromosomal anomaly?

Answer 38

0.6%

Question 39

What are the specimen used for karyotype analysis?

Answer 39

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

Question 40

In what phase are cells arrested for karyotype analysis?

Answer 40

Metaphase

Question 41

What is TTAGGG

Answer 41

Common repeat sequence of telomere

Question 42

What are the short and long arms of chromosomes called?

Answer 42

P and Q arms

Question 43

How is the banding pattern on chromosomes visualized?

Answer 43

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

Question 44

Is chromosome polymorphous an abnormality or normal variation?

Answer 44

Normal variation

Question 45

What is chromosome polymorphism?

Answer 45

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

Question 46

How is euploidy different from aneuoloidy?

Answer 46

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)

Question 47

How are aneuoloidies normally acquired?

Answer 47

Not inherited | Meiotic or mitotic nondisjunction

Question 48

Are aneuoloidies usually compatible with life?

Answer 48

No

Question 49

What is mosaicism and can it be inherited?

Answer 49

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

Question 50

What are the three viable autosomal trisomies?

Answer 50

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

Question 51

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

Answer 51

Patau syndrome

Question 52

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

Answer 52

Down syndrome trisomy 21

Question 53

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

Answer 53

Edwards syndrome | Trisomy 18

Question 54

Why are sex chromosome anomalies usually milder than autosome anomalies?

Answer 54

X inactivation | Limited number of genes on Y

Question 55

How do sex chromosome anomalies occur?

Answer 55

Nondisjunction errors in meiosis

Question 56

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

Answer 56

Pseudoautosomal region

Question 57

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

Answer 57

X inactivation | Limited number of genes on Y

Question 58

How do sex chromosome anomalies occur?

Answer 58

Nondisjunction errors in meiosis

Question 59

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

Answer 59

Pseudoautosomal region