chapter 6 Flashcards
identify the contents of the nucleus
Chromosomes as extended fibers
of chromatin. Nucleoli for rRNA synthesis.
Nucleoplasm as the fluid where
solutes are dissolved.
The nuclear matrix, which is the
protein-containing fibrillar network
explain the structure of the nuclear envlope
The nuclear envelope is a
structure that divides the nucleus
from its cytoplasm.
It consists of two membranes
separated by a nuclear space.
The two membranes are fuses at
sites forming a nuclear pore.
the barrier between the nucleus and the cytoplasm
nuclear envlope
what lines the inner nuclear membrane
lamina
how many proteins does the lamina have and what kind of them
transmembrane proteins and they are 60 distinct proteins
what is the syndrom in which there is amutation in the lamina protein
HGPS
the function of the nuclear lamina is
supports the nuclear envelope and is composed of lamins
how the integrity of the lamina is regulated
phosphorylation/dephosphorylation of intermediate
filaments
what does the dna translation and replication needs
it needs a lot of proteins
what is manifactured in the nucleus
mRNAs, tRNAs, and
ribosomal subunit
what is manufactured in the nucleoi
rRNA
How do proteins and rna moves
passing single-file through the
center of the nuclear pores.
what is the place of the fused two membranes
it is a nuclear pore
what does the nuclear pore have
protein each one is called nucleo porins
how many nucleo porins does it have
The NPC is composed of ~30
proteins called nucleoporins.
how lange is the nuclar complex and the shpe of it
The NPC is a huge complex
(15-30X mass of a ribosome) that exhibits octagonal
symmetry.
is the npc static
The NPC is not static, as many
of its proteins are replaced over
a period of seconds to minutes.
the channel diameter
The channel is 20-to 40-nm
mention the npc components
cytoplasmic filaments
central scaffold
central channel
cytoplasmic ring
nuclear ring
transmembrane ring
fg repat domains
the meaning of fg repeated domains and the use of it
phenylalanine-glycine)
domains that form a
hydrophobic sieve to block
diffusion of macromolecules
greater than 40 KDa
by what are Cytoplasmic proteins are targeted
for the nucleus
nuclear
localization signal (NLS)
types of receptors for the signal
Transport receptors include
importins to move molecules from
the cytoplasm into the nucleus and
exportins to move molecules in the
opposite direction.
how the rna passes
RNAs move through NPCs as RNPs
and carry NES (nuclear export
signals) to pass
how the rna moves
These RNAs move through the NPC as ribonucleoproteins (RNPs).
where are the rnas synthesized and where does it go
These RNAs move through the NPC as ribonucleoproteins (RNPs).
the condition of mrna movement
Only mature, fully processed mRNAs are capable of nuclear export, as an
mRNA with an unspliced intron is retained in the nucleus.
how many avarage base pairs in a mature human on how many chromosomes
6.4 billion base pairs on 46 chromosome
how many dna strand does a chromosome consist of
Each chromosome contains a
single, continuous DNA molecule.
what is the thing that has a widely basic amino acides
histones
the lowest level of chromosome organization is
nucleosomes
the highest level is and when does it happen
meta phase and it s chromosomes
then do we see the chromosomes
in cell division mitosis
the dna and histone are held together by
noncovalent bonds.
Ionic bonds between negatively charged phosphates of the DNA
backbone and positively charged residues of the histones.
talk about the neuclesome to chromosome organization level
Nucleosomes line up end-to-end
into two stacks of nucleosomes
that form a double helical
structure.
Assembly of the 30-nm fiber
increases the DNA- packing ratio
an additional 6-fold, or about 40-
fold altogether.
Maintenance of the 30-nm fiber
depends on interactions between
histone molecules of neighboring
nucleosomes.The 30-nm chromatin fiber is
gathered into a series of large,
supercoiled loops, or domains,
compacted into thicker (80–100
nm) fibers. Among the proteins that may
maintain these DNA loops is
cohesin, best known for holding
replicated DNA molecules
together during mitosis.
other names foe 80-100 filements and which protein makes it
domains supercoiledloops
cohesin
talk about the ratios
A nucleus 10 mm in diameter can
pack 200,000 times this length of
DNA within its boundaries.
Packing ratio of the DNA in
nucleosomes is approximately 7:1.
Assembly of the 30-nm fiber
increases the DNA-packing ratio to
40:1.
Mitotic chromosomes represent the
ultimate in chromatin compactness
with a ratio of 10,000:1.
what happens after the cell mitosis and talk about the kind
After mitosis has been completed, most of the chromatin in highly
compacted mitotic chromosomes returns to its diffuse interphase condition.
Euchromatin returns to a dispersed state after mitosis, heterochromatin
is condensed during interphase.
Constitutive heterochromatin remains condensed all the time. It is found
mostly around centromeres and telomeres and consists of highly repeated
sequences and few genes.
Facultative heterochromatin is inactivated during certain phases of the
organism’s life. It is found in one of the X chromosomes as a Barr body
through X inactivation, a random process that makes adult females genetic
mosaics.
