Nukleus Dan Nukleolus

8/18/2019 Nukleus Dan Nukleolus

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The Nucleus

The nucleus is the headquarters of theThe nucleus is the headquarters of thecell. Itcell. It is the most obvious organelle in

any eukaryotic cell and appears as aa

large dark spot in EUKA!"TI# cells. Itlarge dark spot in EUKA!"TI# cells. Itcontrols all cell activity.controls all cell activity.


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• The Nucleus is a membrane$enclosed organelle %hich house

most of the genetic information

and regulatory machineryresponsible for providing the cell

%ith its unique characteristics.


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Nucleus is the most important organelle in cell.

In mammalian cells& e'cepting (#&

all cells else are the nucleus contained cells.

In prokaryotic cells& there is no membraneto package the nucleic acid substance& so&

%e call this nucleic substance enriched

area as )Nucleoid*.


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The ma+or structures of nucleus include,

① nuclear envelope.

② nucleolus.

③ nuclear matri'.

④ chromatin.

⑤ nuclear lamina.


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The ma+or functions of nucleus,

① inheritance, maintain the geneticcontinuity of generation by the

replication of -NA chromatin and the

proliferation of cell.② development, regulate the cell

differentiation by the regulation of

spatiotemporal sequence of genee'pression.


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• TE NU#/EU0,• 1UN#TI"N0

• It stores the cell2s hereditary material& or -NA.

• 0ite of -NA replication

• 0ite of -NA transcription to mNA

• ibosomal formation

– Nucleolus, NA 3 protein required for ribosomal

synthesis

• It coordinates the cell2s activities& %hich include

gro%th& intermediary metabolism& protein synthesis&and reproduction 4cell division5 by regulating gene

e'pression.


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http://upload.wikimedia.org/wikipedia/commons/3/38/Diagram_human_cell_nucleus.svg


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nuclearpores

chromatin

nucleolus

nuclearenvelope


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nuclearpores

nucleus


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I. Nuclear envelope 4Nuclear membrane5

Nuclear envelope is the lipid bilayer that packages

the nucleus.

Nuclear envelope separates the -NA from cell plasma

and forms a stable inner environment to,

① protect the -NA from damage&

② separate the replication of -NA from the

translation of NA spatiotemporally&

③ the chromatin is anchored on to the nuclear

envelope& that is beneficial to be despiraled&

replicated& condensed& and distributed into ne%nuclei equally&

④ the pores on the envelope are the channels for

the substance e'change.


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Nuclear envelope is bilayer membrane,

Nuclear envelope is composed of

inner nuclear membrane&

outer nuclear membrane& andperinuclear space.

There are nuclear pores on the membrane

that are linked %ith plasma.


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• The inner surface of the NE is bound to

a thin filamentous net%ork 4lamins

polypeptides5 called the nuclearlamina. It provides mechanical support

to the NE and seeves as sites for

attachment for chromatin fibers.

• 9utations in the lamin genes are

responsible for several distinct human

diseases 4e.g. a rare form of muscular

dystrophy5.


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The nuclear pores are the channels for the

substance transportation,

•Nuclear proteins are synthesi:ed in plasma& then

%ill be imported into nucleus by the pores.

•The NAs and the ribosome subunits synthesi:ed

in nucleus %ill be e'ported into plasma by the

pores also.

•In addition& it is indicated by a in+ection

e'periment that small molecules can enter the

nucleus by diffusion from the pores.

TE NU#/EA ;"E


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Nuclear pores are composed of 87 different

nucleoporins at least& and %e call these pore

structure as nuclear pore comple' 4N;#5.

Usually& a mammalian nucleus contains


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The structures of nuclear pore include

① cytoplasmic ring located on the cell

plasma part of the pore comple'contains filaments e'tending into

plasma.

② nuclear ring located on the nuclear

plasma part of the pore comple'

e'tending filaments also.

③ transporter located in center of the

pore as a plug particle.④ 0poke located on the edge of the pore

as the spines.


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•


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The nuclear pore structures on the cell plasma side after an e'traction


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The nuclear pore structures on the nuclear plasma side after an e'traction


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Nuclear plasma protein 4nucleoplasmin5 is

transported by the follo%ing steps,

① The protein combines to the B C D dimer ofthe receptor 4imporin5.

② The comple' of the protein transported

and the receptor used combines to thefilaments located on the N;# cytoplasmic

ring.

③ The filaments curve to the nuclear center&

the transporter structure %ill be changedto form a hydrophilic channel& and the

protein passes through the channel.


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④ The comple' of the protein transported

and the receptor used combines to an$

T;& the comple' is disassembled andreleases out the protein transported.

⑤ The imporin D combined %ith an$T; %ill

be e'ported out of the nucleus& the T;

combined %ith an %ill be hydroly:ed incell plasma& and the an$-; %ill go back

to nucleus to be transformed to an$T;

again.

⑥ The imporin B %ill be transported back to

cell plasma %ith the help from e'portin.


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Fe kno% a little about ho% the macromolecules are

transported to cell plasma from nucleus.

In most of cases& the NA in nucleus iscombined %ith protein to form an N; comple'&

then& transported into cell plasma.

There is nuclear e'portation signal 4NE05 on the

protein of N; comple' that can combine to the

intracellular receptor& e'portin& to form the

comple' of N;$e'portin$an$T;.

In the cell plasma& this comple' %ill bedisassembled and release out the an$T;& NA&

an$-;& e'portin& and N; protein.


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The nucleoplasmin is transported into nucleus


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#hromosome

#hromatin %as named byF. 1lemming in 6=G.

#hromosome %as named by

Faldeyer in 6.

#hromatin and chromosome are

same substance %ith different shape

presentation in different cell cyclephases.


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The chemical components of chromatin,

-NA&

histone protein&

nonhistone protein& andsome NA

at ratio about 6,6,46$6.85,7.78.

-NA,

-NA is the carrier of genetic information.

-NA sequences can be sorted as < types,

nonrepeated fraction&

moderately repeated fraction 4676$6785& and

highly repeated fraction 4H6785.

-NA forms,

($-NA&

$-NA& and

A$-NA.


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-NA forms 4ed color sho%s the couple backbones5


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#hromosome -NA contains three basic sequences,

① autonomously replicating -NA sequence 4A05.

A0 is the starting site of -NA replication.In yeast genome& there are J77$77 A0s

included& and most of them contain a AT

enriched 66bp sequence called as A0

consensus sequence 4A#05.

② centromere -NA sequence 4#EN5 composed of

a lot of repeated sequences.

③ telomere -NA sequence 4TE/5.

TE/ is similar in different bio organisms&

and composed of 8 L 67bp repeated

sequences. uman

TE/ repeated sequence is TTA.


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In 6G


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Three basic sequences of chromosome


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I0T"NE

istone is positively charged and contains

arginine and lycine.istone is alkaline protein.

istones can be sorted as t%o types,

6. ighly conserved core histone including JA&

J(&


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The reasons for that may be as the follo%s,

6. 9ost of the amino acids of core histone

interact %ith -NA or other histones& so&any change of them %ill cause the fatal

mutation.

J. In all bio organisms& the -NA

phosphodiester skeleton that interacts%ith histone is same.

6 is easy to be mutated&

and it is species specific and tissue

specific.


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N"NI0T"NE ;"TEIN,

Nonhistone protein is

the protein that binds to the specific -NA sequence

of chromosome& so& %e call it as sequence specific

-NA binding protein.

The features of nonhistone protein are as the follo%s,

① Nonhistone protein is negatively charged andacidic protein that contains a large number of

aspartic acids and glutamic acids.

② Nonhistone protein can be synthesi:ed during

the %hole cell cycle& but histone protein issynthesi:ed during the 0 phase only.

③ Nonhistone protein can recogni:e the specific

-NA sequence.


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The functions of nonhistone are as the

follo%s,① elp -NA molecules to be pleated

and form different structure

domains that are beneficial to-NA replication and gene

transcription.

②elp to start -NA replicationreaction.

③ egulate transcription and gene

e'pression.


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1"9 -NA T" #"9"0"9E,

There are J< pairs of chromosomes in a human

nucleus.• If you open and e'tend the -NA molecule in

each chromosome& it %ill be 8 cm long.• If you link all -NA molecules in a nucleus

together& it %ill be 6.= L J.7 m long.(ut& the diameter of nucleus is shorter

than 67Mm.

The primary structure formed by the po%erfulcompaction is called as nucleosome.


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Nucleosome,

. Kornberg figured out the model of nucleosome.

Nucleosome is a beaded structure composed of core

particles and linker -NA.

Fe can describe the structure as the follo%s,

① Each nucleosome includes about J77bp -NA& one

histone core& and an 6.② The octameric histone core is composed of

molecules from JA& J(&


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410tructures of nucleosome


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#hromatin -NA filament,

The -NA is compacted to be shortened by =

folds and forms the -NA filament in 66nmdiameter %hen it %as transformed to the beaded

nucleosome chain.

#hromatin -NA e'ists in another style by that the

beaded nucleosome chain is condensed by ?

folds.

Under electron microscope& %e can see the

chromatin -NA filament in


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The -NA filaments in


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For the advanced package of the chromosome, e keep deta!" #nknonso far$ %ro&a&"', !t !s the ser!a" over"apped or p"eated "!ke the fo""os(

From )*+ to hromosome(

)*+ 11nm f!"ament -&eaded n#c"eosome cha!n. 30nm f!"ament

p"eat as "oop cha!n &!nd to the s!tes on n#c"ear ske"eton here !s +/

enr!ched assem&"' of chromosome


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Assembly of chromosome


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eterochromatin and euchromatin,

n the !nter phase -1 and 2. of ce"" c'c"e, the chromat!n !n the n#c"e#s

can &e sorted as heterochromat!n and e#chromat!n$

#chromat!n !s the )*+ reg!ons here the transcr!pt!on !s ver' act!ve$

#chromat!n "ooks "!ke "oose "oop and &r!ght sta!n!ng #nder e"ectron

m!croscope$ #chromat!n !s eas' to &e c"eaved &' n#c"ease at some

h'persens!t!ve s!tes$

eterochromat!n !s condensed !n phase !tho#t an' transcr!pt!on, so, !t

as named as !nact!ve chromat!n$ eterochromat!n !s the genet!c "a' reg!ons,

and rep"!cated "ate"', condensed ear"', that !s ca""ed as heteropyknosis$


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eterochromatin

4dark staining5

and euchromatin

4bright staining5

eterochromatin

Euchromatin


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#onstitutive

hetero$

chromatin !s

hetero

p'knosedchromat!n !n

each t'pe of

ce"" and

"ocated !n

centromere

reg!on$

/he F!g shos

'o# the

onst!t#t!ve

hetero

chromat!nd!sp"a'ed &'

f"#orescence

h'&r!d!at!on !n

s!t#$

1acultative heterochromatin

! h t h t! d


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!s heterochromat!n appeared

!n some spec!a" ce"" t'pe or

deve"op!ng stage$ /he

chromosome of fema"e

mamma"!ans !s the fac#"tat!ve

heterochromat!n$ s#a""',

fema"e mamma"!an ce""

conta!ns do#&"e

chromosomes, and one of

them !s heterochromat!n

ca""ed &arr &od'$ hen ah#man em&r'o !s deve"oped

after 16 da's, one

chromosome !"" &e

transformed as &arr &od' !th

dark sta!n!ng$ o, e can

!dent!f' the se: of a h#manem&r'o &' check!ng the &arr

&od' of the em&r'o ce""s !n the

amn!ot!c f"#!d$

The barr body like a drumstick in a %hite cell


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The structure of chromosome,

n the ; phase of ce"" c'c"e, chromat!n !"" &e transformed as chromosomes

&' the poerf#" condensat!on$ hromosomes are st!ck shape !th d!fferent "ength$

/he metaphase chromosome !s the &est stage to o&serve and n#m&er them&eca#se the morpho"og' of chromosome !s sta&"e at th!s t!me$

/he n#m&er of chromosome !s same !n the same t'pe of ce""s from d!fferent

!nd!v!d#a"s of one spec!es$ /he chromosomes of se: ce""s are hap"o!d, e mark !t

as n$ /he chromosomes of other ce""s are d!p"o!d, e mark !t as 2n$ /he

chromosomes of some ce""s of some spec!es are po"'p"o!d, s#ch as, 4n, 6n, and8n$

/he d!fferent ce""s from same !nd!v!d#a" can &e d!fferent chromosome t'pes$

For e:amp"e, &od' ce""s of rat are 2n, t !ts "!ver ce""s can &e 4n, 8n, and 16n$ /he

chromosome n#m&er of h#man endometr!a" ce"" !s var!a&"e from 2n


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The terms used to the structure of chromosome,

6． #hromatid, ;etaphase chromosome !s composed of to chromat!ds !th a

=#nct!on at the centromere s!te$ ach chromat!d !s formed &' the over"apped and

p"eated )*+ do#&"e strands$ hen the ce"" !s d!v!d!ng the chromat!ds can &e

separated !nto to ne ce""s$J． #hromonema, n the or phase ce""s, each chromonema !nd!cates a

chromat!d$


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The terms of chromosome structure

? N l l i i i 4N" 5 /h th h th


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?． Nucleolar organi:ing regions 4N"s5, /he' are the areas here the genes

for r!&osome >*+ are "ocated$ /he' can s'nthes!e the 28, 18, and 5$8 r>*+

for r!&osome$ *?>s can e:!st !n secondar' constr!ct!on$

=．

0atellite, t !s a &a"" part "ocated at the term!na" of chromosome, and "!nked tothe ma!n part of chromosome &' secondar' constr!ct!on$ /he sate""!te "ocated at

term!na" of chromosome !s ca""ed as term!na" sate""!te, and "ocated &eteen to

secondar' constr!ct!ons !s ca""ed as !ntermed!ate sate""!te$

． Telomere, t !s the spec!a"!ed part "ocated at the term!na" of chromosome$

/he f#nct!on of te"omere !s ma!ntenance of the sta&!"!t' of chromosome$ /e"omere!s composed of the h!gh"' repeated fract!ons, and !t !s so conserved that !t !s

s!m!"ar &eteen the tota""' d!fferent "!fe &e!ngs$ The component of human

telomere is TTA$ /e"omere !s assoc!ated !th ag!ng$ +fter each rep"!cat!on of

te"omere )*+, the te"omere !"" &e shortened &' 50 – 100&p$ /he rep"!cat!on of

te"omere !s droved &' te"omerase that has reverse transcr!ptase act!v!t'$ /h!s

en'me "acks !n norma" ce""s, so, te"omere !"" &ecome short !th the ce""pro"!ferat!on$ o, ce"" !"" &e ag!ng d#r!ng th!s act!on$

III N l l


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III. Nucleolus

*#c"eo"#s ma' &e v!s!&"e !n phase n#c"e#s$ /he' are spher!ca" and 1 – 2 for

each ce"" #s#a""'$ /he n#m&er and s!e of n#c"eo"#s are depended on the ce"" t'pe

and f#nct!on$ /he more prote!ns s'nthes!s and the faster pro"!ferat!on the ce""

takes, the more and &!gger n#c"eo"! the ce"" has$ *#c"eo"#s d!sappears &efore the

ce"" d!v!s!on, and appears !n the end of d!v!s!on$ /he ma=or f#nct!ons of n#c"eo"#s

are r>*+ transcr!pt!on and r!&osome assem&"'$

0tructure of nucleolus,

*o an' mem&rane packages n#c"eo"#s area$ /here are three spec!a" areas

can &e !dent!f!ed #nder e"ectron m!croscope( f!&r!""ar centers -F. that are①s#rro#nded &' dense f!&ers, and "o e"ectr!c dens!t'$ F conta!ns >*+ po"'merase

and r)*+ that !s naked mo"ec#"e$ dense f!&r!""ar component -)F. that !s a "oop②

or ha"f "oop to s#rro#nd F$ /ranscr!pt!on !s carr!ed o#t !n the &order reg!on of F

and )F$ gran#"ar component -. composed of 1520nm part!c"es that are③

the >*%s !n d!fferent man#fact#red steps$ >*% means the >*+ com&!ned !th

prote!n$*#c"eo"#s chromat!ns can &e sorted as to t'pes( heterochromat!n and

e#chromat!n$ /he n#c"eo"#s heterochromat!n !s a"a's "ocated aro#nd the

n#c"eo"#s, so e ca"" them as n#c"eo"#s per!phera" chromat!n$ /he n#c"eo"#s

e#chromat!n !s "ocated !n n#c"eo"#s, and n#c"eo"#s organ!!ng reg!on !n that the

r)*+ !s "ocated$


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0tructure of nucleolus

I ib


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I. ibosome

>!&osome !s the man#fact#r!ng shop to s'nthes!e prote!ns$ /here are a&o#t

20,000 r!&osomes !n an act!ve"' gro!ng &acter!#m$ >!&osome prote!ns are 10@ of

tota" prote!ns of ce"", and !ts >*+ !s 80@ of ce"" tota" >*+$

0tructure of ribosome,

/he rat!os of prote!n and >*+ to r!&osome components are 40@ and 60@$

/he r!&osome s#n!ts are composed of the com&!nat!on of the prote!n and >*+$

/he cata"'t!c act!v!t!es needed &' the trans"at!on are presented &' r!&osome

prote!n, r>*+ and other he"per factors$

/he r!&osomes can &e sorted as to t'pes$ 70 r!&osome e:!sts !n &acter!a,m!tochondr!on, and ch"orop"ast$ 80 r!&osome e:!sts !n the p"asma of e#kar'ot!c

ce""s$

>!&osome !s composed of a "arge s#n!t and a sma"" s#n!t$ /he &oth

s#n!ts !"" &e com&!ned together hen the r!&osome s'nthes!es prote!n !th

m>*+ as temp"ate$ +fter the trans"at!on, the r!&osome !"" &e separated as to

parts aga!n$ hen a prote!n !s trans"ated on an m>*+, man' r!&osomes can &!ndto the m>*+ to s'nthes!e the prote!n$ e ca"" these r!&osomes for one prote!n

s'nthes!s as polyribosome$ /he "onger m>*+ !s #sed, the more r!&osomes are

com&!ned$ /he po"'r!&osome enhances the eff!c!enc' of prote!n s'nthes!s$

%rokar'ot!c 5 r>*+ and e#kar'ot!c 5$8 r>*+ are ver' conserved for the!r

str#ct#res, so, the' can &e #sed to research the &!oevo"#t!on$


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Assembly of ribosome,

/he )*+ fragment encod!ng r>*+ !s ca""ed as r>*+ gene$ /here are a&o#t

200 cop!es of th!s gene !n a h#man ce""$ r)*+ conta!ns no h!stone core, so, !t !s a

naked )*+$/o transcr!pt r>*+, the >*+ po"'merase moves ahead a"ong the )*+

mo"ec#"e$ /he s'nthes!ed r>*+ mo"ec#"es e:tend o#t the!r mo"ec#"es from the

comp"e: of po"'merase and )*+, and form a feather"!ke str#ct#re #nder

m!croscope$


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r>*+ transcr!pt!on

/he f!"aments are the

ne s'nthes!ed 45

r>*+ that com&!nes to

prote!n to form >*%

comp"e:$ /hemeth'"ated 45 r>*+

can &e c"eaved as the

to parts &' >*ase(

18 r>*+ and 32

r>*+， the "atter !s

c"eaved as 28 r>*+and 5$8 r>*+$ /he

s'nthes!ed 5 r>*+

!"" &e transported !nto

n#c"eo"#s to =o!n the

assem&"' of the "arge

s#n!ts of r!&osome$

There is a ?7bp non$transcription -NA

fragment bet%een ad+acent rNA genes


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Assembly of ribosome


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. Nuclear matri'

*#c"ear matr!: !s ca""ed as n#c"eoske"eton that !s a meshork !n e#kar'ot!c

ce""s, that !s hat to"d 'o# &efore$ Beca#se n#c"ear matr!: !s assoc!ated !th

)*+ rep"!cat!on, >*+ transcr!pt!on and mod!f!cat!on, chromosome assem&"', andv!r#s rep"!cat!on, n#c"ear matr!: !s no pa!d more attent!ons to$

#omponents of nuclear matri',

① *onh!stone f!"aments at rat!o of 96@$ /he n#c"eoske"eton conta!ns three

scaffo"d prote!ns( , , and $Ⅰ Ⅱ Ⅲ

② + "!tt"e >*+ and )*+( /he >*+ !s !mportant to ma!nta!n the ske"eton

str#ct#re$ /he )*+ !s ca""ed as matr!: Ascaffo"d assoc!ated reg!on -;+> or +>.

here the +/ !s enr!ched to form the heterochromat!n &!nd!ng s!tes$

③ + "!tt"e phospho"!p!ds -1$6@. and s#gars -0$9@.$

*#c"ear ske"eton – n#c"ear "am!na – !nter f!"aments – pore comp"e: !s a

meshork s'stem !th ver' good sta&!"!t'$


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The function of nuclear skeleton,

1$ %resent the scaffo"ds for )*+ rep"!cat!on$ )*+ can &e anchored on to the

scaffo"d !th a rep"!cat!on "oop$ /he en'mes needed &' )*+ rep"!cat!on are

"ocated on the ske"eton, s#ch as )*+ po"'merase C, )*+ pr!merase, )*+

topo!somerase $

2$ s the p"ace here gene can &e transcr!pted and mod!f!ed$ /here are >*+

po"'merase &!nd!ng s!tes on the ske"eton$ *e s'nthes!ed >*+ !s com&!nedto the ske"eton for f#rther mod!f!cat!on$

3$ s assoc!ated !th the assem&"' of chromosome$ /he n#c"ear ske"eton ma'

&e same th!ng to chromosome ske"eton$ 30nm chromat!n f!&ers are

com&!ned to n#c"ear ske"eton to form "oops that !"" &e packaged f#rther !n ;

phase to &e assem&"ed as chromosome$


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#hromatin bound on nuclear skeleton or chromosome skeleton

Nukleus Dan Nukleolus

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