9 Flashcards
1
Q
Facts about the Nucleus
Prokaryotes have no _________
A
nucleus
2
Q
Facts about the Nucleus
Eukaryotes generally have 1 nucleus except for _______, _________, and _________
A
rbcs, osteoclasts and skeletal muscles
3
Q
Facts about the Nucleus
_________ to be discovered
A
First organelle
4
Q
Facts about the Nucleus
First described by ________ in 1804
A
Franz Bauer
5
Q
Facts about the Nucleus
Presented by Scottish botanist, _________
during the 1831 meeting of the Linnaean
Society of London
A
Robert Brown
6
Q
Overall functions of the nucleus
Storage of ___________
A
genetic material
7
Q
Overall functions of the nucleus
Controls ___________
A
cell growth and reproduction
8
Q
Overall functions of the nucleus
Home of essential _______ (i.e.
replication, transcription )
A
cellular processes
9
Q
Overall functions of the nucleus
Regulates passage of materials _________ of nucleus (RNA, ions, nucleotides,aa etc)
A
in and out
10
Q
Overall functions of the nucleus
Regulates passage of materials in and out of
nucleus (____, _____, ____, ____)
A
RNA, ions, nucleotides,aa etc
11
Q
depending on nature
and size of molecules
A
active vs passive transport
12
Q
Nucleus: Structure
About ________ of the cell volume
A
10%
13
Q
Nucleus: Structure
Has a __________, two leaflets 10-50 nm apart
A
double membrane
14
Q
Nucleus: Structure
Has a double membrane, _________ 10-50 nm apart
A
two leaflets
15
Q
Nucleus: Structure
Has a double membrane, two leaflets 10-50 nm apart
*This forms an ___________
A
interior space
16
Q
Nucleus: Structure
- About 10% of the cell volume
– Has a double membrane, two leaflets 10-50 nm apart
*This forms an interior space
*The space is continuous with the interior of the __________
A
rough endoplasmic reticulum
17
Q
Parts of the Nucleus
made of phospholipid bilayer
A
Nuclear envelope
18
Q
Parts of the Nucleus
Nuclear envelope separates?
A
cytoplasm and nucleoplasm
19
Q
Parts of the Nucleus
Inner and outer membrane separated by __________
A
perinuclear space
20
Q
Parts of the Nucleus
Outer nuclear membrane continuous with RER and studded with __________
A
ribosomes
21
Q
Parts of the Nucleus
Contains 3000 ____________
A
nuclear pores
22
Q
Parts of the Nucleus
Contains 3000 nuclear pores,
regulated by a protein structure,
the _____________
A
nuclear pore complex
23
Q
Parts of the Nucleus
Small molecules (<mw 20,000)
can pass right through, larger
molecules are strongly
regulated.
A
nuclear pore complex
24
Q
Parts of the Nucleus
Interior of envelope supported
by ___________ (on the
nucleoplasm side)
A
nuclear lamina
25
**Parts of the Nucleus**
A network of 10nm-diameter
protein fiber: __________
lamins
26
**Parts of the Nucleus**
proteins that form the nuclear lamina, a mesh-like structure that provides mechanical stability to the nuclear envelope
lamins
27
**Parts of the Nucleus**
Three (3) functions of lamins
(1) reinforces structure of the nucleus
(2) anchors chromatin
(3) impt in replication and transcription
28
**Parts of the Nucleus**
An Integral membrane
Nuclear Pore
29
**Nucleus: Structure**
Interior of the nucleus
nucleoplasm
30
**Nucleus: Structure**
analogous to cytoplasm
nucleoplasm
31
**Nucleus: Structure**
*Interior of the nucleus*
Includes the soluble protein
____________
nucleoplasmin
32
**Nucleus: Structure**
*Interior of the nucleus*
____________, sticky
fluid that supports chromosomes and nucleolus
Highly gelatinous
33
**Nucleus: Structure**
*Interior of the nucleus*
Highly gelatinous, sticky
fluid that supports
_____________
chromosomes and nucleolus
34
**Nucleus: Structure**
*Interior of the nucleus*
_____________ for
organelles inside nucleus
Suspension substance
35
**Nucleus: Structure**
*Interior of the nucleus*
Also dissolved are
__________________
nucleotides and enzymes
36
**Nucleus: Parts**
a network of protein fibers that support and organize the chromatin and other structures
nuclear matrix
37
– Active chromatin
(euchromatin) appear
lighter,
– Inactive chromatin
(heterochromatin) is darker
and located near periphery
of nucleus
chromatin
38
**Chromatin**
Active chromatin (_________) appear lighter
euchromatin
39
**Chromatin**
Inactive chromatin
(_____________) is darker
and located near periphery
of nucleus
heterochromatin
40
Active chromatin
euchromatin
41
appear lighter
euchromatin
42
Inactive chromatin
heterochromatin
43
is darker and located near periphery of nucleus
heterochromatin
44
a granular region
Nucleolus
45
site of ribosome assembly
Nucleolus
46
**Functions of Chromatin**
Chromatin determines ________
chromosome structure
47
**Functions of Chromatin**
Changes __________ associated with cell division
chromosome structures
48
**Functions of Chromatin**
Changes chromosome structures associated with __________
cell division
49
**Functions of Chromatin**
Regulates ___________
chromosome function
50
There are two types of heterochromatin
1) Constitutive heterochromatin
2) Facultative heterochromatin
51
* Regions that are always heterochromatic
* Permanent part of the genome and not convertible to euchromatin
* Permanently inactive with regard to transcription
Constitutive heterochromatin
52
**Constitutive heterochromatin**
Regions that are _______ heterochromatic
always
53
**Constitutive heterochromatin**
Permanent part of the _______ and not convertible to euchromatin
genome
54
**Constitutive heterochromatin**
Permanent part of the genome and _________ to euchromatin
not convertible
55
**Constitutive heterochromatin**
________ with regard to transcription
Permanently inactive
56
**Constitutive heterochromatin*
Permanently inactive with regard to _________
transcription
57
* Regions that can interconvert between euchromatin and
heterochromatin
* Takes on staining and compactness characteristics of heterochromatin
during some phases of development
* Example: Barr body
Facultative heterochromatin
58
**Facultative heterochromatin**
Regions that _________ between euchromatin and
heterochromatin
can interconvert
59
**Facultative heterochromatin**
Regions that can interconvert between _________
euchromatin and heterochromatin
60
**Facultative heterochromatin**
Takes on staining and compactness characteristics of heterochromatin
during some phases of _______
development
61
Example: Barr body
Facultative heterochromatin
62
In all cells of _________, one of the two X chromosomes is
permanently inactivated and
does not participate in
transcription.
female
individuals
63
In all cells of female
individuals, __________ X
chromosomes is
permanently inactivated and
does not participate in
transcription.
one of the two
64
In all cells of female
individuals, one of the two X
chromosomes is
____________ and
does not participate in
transcription.
permanently inactivated
65
In all cells of female
individuals, one of the two X
chromosomes is
permanently inactivated and
does not participate in
____________.
transcription
66
The _____________
is recognizable in epithelial
cells from the oral cavity as a
single granule called sex
chromatin (Barr body) that is
attached to the nuclear
lamina.
inactive X chromosome
67
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
68
**The Nucleolus**
_________ of volume of nucleus
25%
69
**The Nucleolus**
Site of __________
ribosome biogenesis
70
**The Nucleolus**
Form around specific chromosome regions known as _________
NOR
71
**The Nucleolus**
NOR
nucleolus organizer regions
72
**The Nucleolus**
Main function: combine rRNA + protein to form _______________
incomplete ribosome
73
**The Nucleolus**
Main function: combine _______ to form incomplete ribosome
rRNA + protein
74
**The Nucleolus**
Uninterrupted chain from nucleoplasm to
interior of nucleolus (_________) allow
macromolecules up to 2000 kd to circulate
through organelle
nucleolar passages
75
A Single Set of Human DNA is > __________
1 Meter in Length
76
**CHROMATIN CONDENSATION**
Results from ________ of chromatin
packaging
77
**CHROMATIN CONDENSATION**
________ stops
Transcription
78
**CHROMATIN CONDENSATION**
Chromosomes visible in ____
microscopy
79
**CHROMATIN CONDENSATION**
Separation of _______ sets occurs in nuclear division
haploid chromosome
80
**CHROMATIN CONDENSATION**
Separation of haploid
chromosome sets occurs in
_____________
nuclear division
81
**CHROMATIN CONDENSATION**
Packaging ratio about _________
10000:1
82
**Importance of Folded DNA Structures**
a. for storage in the _______ of the nucleus
limited size
83
**Importance of Folded DNA Structures**
b. during ___________, it allows for neat segregation into newly formed cells
mitosis and meiosis
84
**Importance of Folded DNA Structures**
b. during mitosis and meiosis, it allows for neat segregation into _________
newly formed cells
85
**Importance of Folded DNA Structures**
c. manner of folding determines _________ in a cell
activity of genes
86
basic structural unit of eukaryotic chromosome
Nucleosome
87
**Nucleosome**
- an octamer composed of two each of _________ histone proteins
H2A, H2B, H3 and H4
88
**Nucleosome**
DNA wrapped around _______ and H1 stabilizes association of
nucleosomes to form solenoid
octamer
89
**Nucleosome**
DNA wrapped around octamer and ________ stabilizes association of nucleosomes to form solenoid
H1
90
**Nucleosome**
DNA wrapped around octamer and H1 stabilizes association of
nucleosomes to form __________
solenoid
91
is a complex of a histone and 146 nucleotide pairs
a nucleosome
92
All histone proteins have a large positive charge; between 20
and 30% of their sequences consist of the basic _________
amino acids, lysine and arginine.
93
Histones will bind very strongly to the ___________ in forming chromatin.
negatively charged DNA
94
-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
Histones
95
first to form, tightly bound, most conserved
H3, H4
96
well conserved with species-specific variation
H2A, H2B,
97
The compaction of linear DNA in eukaryotic chromosomes
involves interactions between _________
DNA and various proteins
98
Proteins bound to DNA are subject to change during the life ofthe cell
* These changes affect the _______
degree of chromatin compaction
99
how the cell moves molecules into and out of the nucleus
Nuclear Pores
100
At the nuclear pore, the inner and outer membranes come
together forming an _______
opening
101
Nuclear pores is lined with _____
protein
102
It is lined with protein
– at least ________ proteins
100 nucleoporin
103
It is lined with protein
– at least 100 nucleoporin proteins
– Including ___________, extending to the cytoplasm
cytoplasmic filaments
104
It is lined with protein
– at least 100 nucleoporin proteins
– Including cytoplasmic filaments, extending to the _________
cytoplasm
105
* Proteins are brought into the ___________
– and can be sent out too
nucleus from the cytoplasm
106
RNAs (_____________)
are all transported out of the nucleus
– but only when they are completed
messenger RNA, ribosomal RNA and transfer RNAs
107
- 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 –
Nuclear Location Signal (NLS)
108
a specific amino acid sequence marks protein for
nuclear entry
(Laskey, 1982)
109
a series of positively charged amino acids in specific
sequence:
pro – lys – lys – lys – arg – lys – val –
110
NLS
Nuclear Location Signal
111
**how do we know the function of the NLS?**
Experiment 1:
– modify the amino acid sequence (by site-directed-mutagenesis)
* “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-arglys-val-) completely prevents accumulation in the nucleus.
112
what happens when we alter the NLS?
Altering the nuclear localization signal (NLS) can disrupt the transport of proteins into the nucleus, potentially leading to a loss of function or misregulation of cellular processes. This change may affect gene expression, signaling pathways, and overall cellular homeostasis.
113
What happens when we use recombinant DNA techniques to add the NLS to a dummy protein?
Adding a nuclear localization signal (NLS) to a dummy protein using recombinant DNA techniques allows that protein to be transported into the nucleus of cells. This modification can enable the protein to interact with nuclear targets, influencing various cellular processes such as gene regulation or signaling.
114
* What happens when we use recombinant DNA techniques
to add the NLS to a dummy protein?
* Normal or modified ________ (NLS added)
and injected to the cytoplasm
Bovine Serum Albumin
115
family of proteins
associated with the
nuclear pore
complex
nuclear transport
receptors
116
recognize
the NLS and bring
proteins in
Importins
117
Another set of
proteins, the
_________, work in the
opposite direction
– These recognize
other signals
exportins
118
**mechanism of protein import through nuclear pore complex**
(1) Protein binds to a two-protein complex (______________)
- Importin a is a receptor for the NLS portion of the
protein
i.e. it recognizes and sticks to this region.
(2) Complex and protein stick to cytoplasmic filament
- mediated by importin b
(importin a and
importin b
119
**mechanism of protein import through nuclear pore complex**
is a receptor for the NLS portion of the
protein
- Importin a
120
**mechanism of protein import through nuclear pore complex**
(2) Complex and protein stick to cytoplasmic filament
- mediated by ____________
importin b
121
**mechanism of protein import through nuclear pore complex**
(3) Complex moves into nucleoplasm
- Not an energy consuming step, it can go back at this
point unless captured by the _______ in next step:
RanGTP
122
**mechanism of protein import through nuclear pore complex**
(4) Complex binds to another protein (Ran-GTP)
- After binding, ________
- importin b ______ on the Ran-GTP
complex dissociates
stays
123
**mechanism of protein import through nuclear pore complex**
(5) _________ - importin b complex moves back to the cytoplasm,
down a concentration gradient
Ran-GTP
124
**mechanism of protein import through nuclear pore complex**
(5) Ran-GTP - importin b complex moves back to the cytoplasm,
________________
down a concentration gradient
125
**mechanism of protein import through nuclear pore complex**
(6) Two things happen now:
– (1) the Ran-GTP is converted to Ran-GDP + Pi by the enzyme
________. This causes it to loosen from importin b
RANGAP
126
**mechanism of protein import through nuclear pore complex**
an _________ molecule binds to importin a, setting it up for
transport out of the nucleus
exportin
127
**mechanism of protein import through nuclear pore complex**
(7) Ran-GDP _______ back to the nucleus (1)
– (down its concentration gradient, I.e. from high to low
concentration)
– Exportin carries importin a out of the nucleus (2)
diffuses
128
**mechanism of protein import through nuclear pore complex**
(8) Restoration to initial state
– The importin a and importin b complex reforms.
– Enzyme _________ re-forms Ran-GDP to RanGTP
RCC1
129
_________ is an energy source and controls
the process
GDP to GTP conversion
130
Molecules always diffuse from high to low concentration, so
if the gradient is maintained, it can be used to bring __________ back to the cytoplasm
importin b
131
RCC1 occurs only in the ________
nucleoplasm
132
RANGAP occurs in _________
cytoplasm
133
RCC1 occurs only in the nucleoplasm, RANGAP in cytoplasm
- By breaking down Ran-GTP and thereby removing it,
RANGAP _______ the concn gradient. It can take the
other molecule out with it.
maintains
134
By changing Ran-GDP back to Ran-GTP, RCC1 maintains
the gradient helping Ran-GDP to diffuse back into the
______
nucleus
