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BIO107- CELL AND MOLECULAR BIOLOGY > Lecture 4: Nucleus > Flashcards

Lecture 4: Nucleus Flashcards

1
Q

Parts of the Nucleus

A
  • Nuclear Envelope
    -Nuclear Pore
  • Nucleoplasm
    -Nucleolus
  • DNA (Chromatin)
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2
Q

-made of phospholipid bilayer
-separates cytoplasm and nucleoplasm
-Inner and outer membrane separated by perinuclear space
-Outer nuclear membrane continuous with RER and studded with ribosomes

A

Nuclear envelope

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3
Q

a network of protein fibers that support and organize the chromatin and other structures

A

Nuclear Matrix

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4
Q

2 types of Chromatin

A

-Active Chromatin
-Inactive Chromatin

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5
Q

Appear Lighter

A

Active Chromatin

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6
Q

Active Chromatin

A

euchromatin

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7
Q

is darker
and located near periphery
of nucleus

A

Inactive chromatin

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8
Q

Inactive chromatin

A

heterochromatin

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9
Q

*a granular region
*site of ribosome
assembly

A

Nucleolus

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10
Q

two types of heterochromatin

A

-Constitutive heterochromatin
-Facultative heterochromatin

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11
Q
  • Regions that are always heterochromatic
  • Permanent part of the genome and not convertible to euchromatin
  • Permanently inactive with regard to transcription
A

Constitutive heterochromatin

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12
Q
  • Regions that can interconvert between euchromatin and
    heterochromatin
  • Takes on staining and compactness characteristics of heterochromatin
    during some phases of development
  • Example: Barr body
A

Facultative heterochromatin

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13
Q

Heterochromatin lies against the __________ in patches and is broken up at the site of the __________.

A

-Nuclear Envelope
-Nuclear pore

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14
Q
  • Results from packaging of
    chromatin
  • Transcription stops
  • Chromosomes visible in
    microscopy
  • Separation of haploid
    chromosome sets occurs in
    nuclear division
  • Packaging ratio about 10000:
A

CHROMATIN CONDENSATION

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15
Q

basic structural unit of eukaryotic
chromosome

A

Nucleosome

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16
Q

Nucleosome is an octamer composed of two each of __, ___, ___, and ___ histone proteins

A

H2A, H2B, H3 and H4

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16
Q

DNA wrapped around octamer and H1 stabilizes association of nucleosomes to form _________

A

solenoid

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17
Q

A nucleosome is a complex of a _______ and _____________

A

histone and 146 nucleotide pairs

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18
Q

-highly conserved sequences (universality in eukaryotes)
- H3, H4 first to form, tightly bound, most conserved
- H2A, H2B, well conserved with species-specific variation
-H1 divergent, absent in S. cerevesiae

A

Histones

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19
Q

The compaction of linear DNA in eukaryotic chromosomes involves interactions between ______ and ______________

A

DNA and various proteins

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20
Q

Proteins bound to DNA are subject to change during the life of the cell. These changes affect the _______________________

A

degree of chromatin compaction

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21
Q

Proteins are brought into the nucleus from the cytoplasm, and can be sent out too by __________

A

Nuclear Pore

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22
Q

RNAs (messenger RNA, ribosomal RNA and transfer RNAs) are all transported out of the nucleus but only when they are _________

A

completed

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23
Q

– a specific amino acid sequence marks protein for nuclear entry (Laskey, 1982)
– a series of positively charged amino acids in specific sequence: (pro – lys – lys – lys – arg – lys – val –)

A

Nuclear Location Signal (NLS)

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24
family of proteins associated with the nuclear pore complex
nuclear transport receptors
25
Example of Nuclear transport receptors mentioned in the PPT
Importin and Exportin
26
recognize the NLS and bring proteins into the nucleus
Importin
27
Work in the opposite direction with importin. These recognize other signals
Exportin
28
__________ have no nucleus
Prokaryotes
29
The nucleus is About _______ of the cell volume
10%
29
Eukaryotes generally have 1 nucleus except for ____, _______and ______________
rbcs, osteoclasts and skeletal muscles
29
-nucleus is the first organelle to be discovered -First described by _______________
Franz Bauer in 1804
29
Overall Function of the Nucleus
-Storage of genetic material -Controls cell growth and reproduction -Home of essential cellular processes (i.e. replication, transcription ) - Regulates passage of materials in and out of nucleus (RNA, ions, nucleotides, aa etc)
30
The Nucleus contains __________ nuclear pores, regulated by a protein structure, the ____________.
-3000 -nuclear pore complex
30
The discovery of nucleus was presented by Scottish botanist, ___________ during the 1831 meeting of the Linnaean Society of London
Robert Brown
31
In the nuclear pore __________ (
-small molecules - larger molecules
32
The Interior of nuclear envelope is supported by _______________ ( on the nucleoplasm side)
nuclear lamina
33
A network of 10nm-diameter protein fiber
Lamins
34
3 Functions of nuclear Lamina
(1)reinforces structure of the nucleus, (2) anchors chromatin (3) important in replication and transcription
34
*analogous to cytoplasm * Includes the soluble protein nucleoplasmin * Highly gelatinous, sticky fluid that supports chromosomes and nucleolus * Suspension substance for organelles inside nucleus * Also dissolved are nucleotides and enzyme
Nucleoplasm
35
Nucleoplasm includes soluble protein called?
nucleoplasmin
36
Functions of Chromatin
* Determines chromosome structure * Changes chromosome structures associated with cell division * Regulates chromosome function
37
In all cells of female individuals, one of the two X chromosomes is permanently _________ and ________________________ in transcription.
-inactivated -does not participate
38
The inactive X chromosome is recognizable in epithelial cells from the oral cavity as a single granule called ___________________ that is attached to the nuclear lamina
sex chromatin (Barr body)
39
In _____________, the sex chromatin takes the form of a drum stick-like appendage to the nucleus. These structures have been used for gender testing
neutrophils
40
-25% of volume of nucleus -Site of ribosome biogenesis -Form around specific chromosome regions known as NOR
Nucleolus
41
Main function of the Nucleolus
combine rRNA + protein to form incomplete ribosome
42
Uninterrupted chain from nucleoplasm to interior of nucleolus (nucleolar passages) allow macromolecules up to ___________ to circulate through organelle
2000 kd
43
Importance of Folded DNA Structures
a. for storage in the limited size of the nucleus b. during mitosis and meiosis, it allows for neat segregation into newly formed cells c. manner of folding determines activity of genes in a cell
44
All histone proteins have a large positive charge; between 20 and 30% of their sequences consist of the____________, _____________and _____________
-basic amino acids, -lysine -arginine
45
Histones are large positive charge, meaning histones will bind very strongly to the _______________ in forming chromatin.
negatively charged DNA
46
* At the pore, the inner and outer membranes come together forming an opening. * It is lined with protein
Nuclear Pore
47
Nuclear Pores contains at least ________ proteins, including _____________, extending to the cytoplasm.
-100 Nucleoporins -Cytoplasmic Filaments
48
Nuclear Pores regulate traffic into and out of the nucleus by means of the _________________
Nuclear Location Signal (NLS)
49
How do we know the function of NLS ?(Experiment 1)
modify the amino acid sequence (by site-directed-mutagenesis)
50
Modifying the amino acid sequence (by site-directed-mutagenesis). Process and conditions:
* “SV40 virus t-antigen” a protein molecule, M.W. 90,000 * normally enters the nucleus if injected into cytoplasm. * normally accumulates in the nucleus (one-way) * experimentally visualize the location of the protein – using a fluorescent tag which glows under UV light – Set up a microscope with ultraviolet light source * An experimental alteration of the sequence (pro-lys-thr-lys-arg-lys-val-) completely prevents accumulation in the nucleus
51
What happens when we use recombinant DNA techniques to add the NLS to a dummy protein?
Adding an NLS to a dummy protein using recombinant DNA techniques allows the protein to be transported into the nucleus of a cell, where it can perform its intended function. Example of this is Normal or modified Bovine Serum Albumin (NLS added) and injected to the cytoplasm
52
Protein binds to a two-protein complex. Which are?
importin a (Alpha) and importin b (beta)
53
___________ is a receptor for the NLS portion of the protein (i.e. it recognizes and sticks to this region.)
Importin a (alpha)
53
Complex and protein stick to cytoplasmic filament is mediated by _____________
importin b (beta)
54
- Not an energy consuming step, it can go back at this point unless captured by the RanGTP in next step
Complex moves into nucleoplasm
55
importin b stays on the ____________ after binding and complex dissociation.
Ran-GTP
56
Ran-GTP - importin b complex moves back to the cytoplasm, ________________
down a concentration gradient
56
the Ran-GTP is converted to____________ by the enzyme ______. This causes it to loosen from importin b
- Ran-GDP + Pi -RANGAP
57
an exportin molecule binds to ___________, setting it up for transport out of the nucleus
importin a
58
Enzyme _______ re-forms Ran-GDP to Ran-GTP
RCC1
59
Mechanism of Protein complex through nuclear pore complex
1. Protein binds to a two-protein complex (importin a and importin b) 2. Complex and protein stick to cytoplasmic filament 3. Complex moves into nucleoplasm 4. Complex binds to another protein (Ran-GTP) 5. Importin b complex moves back to the cytoplasm, down a concentration gradient 6. the Ran-GTP is converted to Ran-GDP + Pi by the enzyme RANGAP. This causes it to loosen from importin b 7. an exportin molecule binds to importin a, setting it up for transport out of the nucleus 8. Ran-GDP diffuses back to the nucleus 9. Restoration to initial state
60
___________ is an energy source and controls the process
GDP to GTP conversion
61
Molecules always diffuse from high to low concentration, so if the gradient is maintained, it can be used to __________________________
bring importin b back to the cytoplasm
62
RCC1 occurs only in the _________, RANGAP occurs in ___________
-nucleoplasm -cytoplasm
63
By breaking down ________ and thereby removing it, RANGAP maintains the concentration gradient. It can take the other molecule out with it.
Ran-GTP
64
By changing _________ back to Ran-GTP, RCC1 maintains the gradient helping _______ to diffuse back into the nucleus
Ran-GDP

BIO107- CELL AND MOLECULAR BIOLOGY (13 decks)

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