chapter 6

Question 1

identify the contents of the nucleus

Answer 1

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

Question 2

explain the structure of the nuclear envlope

Answer 2

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.

Question 3

the barrier between the nucleus and the cytoplasm

Answer 3

nuclear envlope

Question 4

what lines the inner nuclear membrane

Answer 4

lamina

Question 5

how many proteins does the lamina have and what kind of them

Answer 5

transmembrane proteins and they are 60 distinct proteins

Question 6

what is the syndrom in which there is amutation in the lamina protein

Answer 6

HGPS

Question 7

the function of the nuclear lamina is

Answer 7

supports the nuclear envelope and is composed of lamins

Question 8

how the integrity of the lamina is regulated

Answer 8

phosphorylation/dephosphorylation of intermediate
filaments

Question 9

what does the dna translation and replication needs

Answer 9

it needs a lot of proteins

Question 10

what is manifactured in the nucleus

Answer 10

mRNAs, tRNAs, and
ribosomal subunit

Question 11

what is manufactured in the nucleoi

Answer 11

rRNA

Question 12

How do proteins and rna moves

Answer 12

passing single-file through the
center of the nuclear pores.

Question 13

what is the place of the fused two membranes

Answer 13

it is a nuclear pore

Question 14

what does the nuclear pore have

Answer 14

protein each one is called nucleo porins

Question 15

how many nucleo porins does it have

Answer 15

The NPC is composed of ~30
proteins called nucleoporins.

Question 16

how lange is the nuclar complex and the shpe of it

Answer 16

The NPC is a huge complex
(15-30X mass of a ribosome) that exhibits octagonal
symmetry.

Question 17

is the npc static

Answer 17

The NPC is not static, as many
of its proteins are replaced over
a period of seconds to minutes.

Question 18

the channel diameter

Answer 18

The channel is 20-to 40-nm

Question 19

mention the npc components

Answer 19

cytoplasmic filaments
central scaffold
central channel
cytoplasmic ring
nuclear ring
transmembrane ring
fg repat domains

Question 20

the meaning of fg repeated domains and the use of it

Answer 20

phenylalanine-glycine)
domains that form a
hydrophobic sieve to block
diffusion of macromolecules
greater than 40 KDa

Question 21

by what are Cytoplasmic proteins are targeted
for the nucleus

Answer 21

nuclear
localization signal (NLS)

Question 22

types of receptors for the signal

Answer 22

Transport receptors include
importins to move molecules from
the cytoplasm into the nucleus and
exportins to move molecules in the
opposite direction.

Question 23

how the rna passes

Answer 23

RNAs move through NPCs as RNPs
and carry NES (nuclear export
signals) to pass

Question 24

how the rna moves

Answer 24

These RNAs move through the NPC as ribonucleoproteins (RNPs).

Question 25

where are the rnas synthesized and where does it go

Answer 25

These RNAs move through the NPC as ribonucleoproteins (RNPs).

Question 26

the condition of mrna movement

Answer 26

Only mature, fully processed mRNAs are capable of nuclear export, as an
mRNA with an unspliced intron is retained in the nucleus.

Question 27

how many avarage base pairs in a mature human on how many chromosomes

Answer 27

6.4 billion base pairs on 46 chromosome

Question 28

how many dna strand does a chromosome consist of

Answer 28

Each chromosome contains a
single, continuous DNA molecule.

Question 29

what is the thing that has a widely basic amino acides

Answer 29

histones

Question 30

the lowest level of chromosome organization is

Answer 30

nucleosomes

Question 31

the highest level is and when does it happen

Answer 31

meta phase and it s chromosomes

Question 32

then do we see the chromosomes

Answer 32

in cell division mitosis

Question 33

the dna and histone are held together by

Answer 33

noncovalent bonds.
Ionic bonds between negatively charged phosphates of the DNA
backbone and positively charged residues of the histones.

Question 34

talk about the neuclesome to chromosome organization level

Answer 34

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.

Question 35

other names foe 80-100 filements and which protein makes it

Answer 35

domains supercoiledloops
cohesin

Question 36

talk about the ratios

Answer 36

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.

Question 37

what happens after the cell mitosis and talk about the kind

Answer 37

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.