4. dna 2010-2
TRANSCRIPT
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DNA - RNA
Dra Sri Musta’ina, MKes. 21 September2010
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Structure of The Nucleic Acid
Molecule size > protein
Synthesized at : cell nuclei; mitochondria; plastid
Nucleic Acid is polymers of Nucleotides :
DNA & RNA
Each nucleotide consist of :1 !entose su"ar
Ri#ose su"ar RNA
Deo$yri#ose su"ar DNA% Nitro"enous #ase
!urine!yrimidine
!hosphate
'unction : as "enetic material
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Organization of uman DNA
Size of DNA molecules :
haploid cells : 3,0 x 109 base pairs
1 chromosome
∞ 7 cm in len!h
!o!al len!h " #$ chromosomes% 1,7 m&
'unc!ion :
As (ene!ic )a!erial
1& Able !o replica!e
*& Able !o encode !he se+uence of pro!ein
3& Able !o chane in a con!rolled a-
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- DNA interacts with basic proteins known as histones
- Histones arginine and lysine
- Five classes of histones : H1, H2A, H2, H! and H"
H2A H2 #llipsoid
H!
H"
- $ther types of proteins are also associated with DNA
- N%cleoso&es :
' bead-like str%ct%res of DNA
' DNA coils aro%nd the s%rface of the
ellipsoid
' (o&ple) of histones pl%s DNA
!a"#ing of DNA in "e$$s
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Deo%&ribonu"$ei" A"i' ( DNA )
Nucleo!ide S!ruc!ure :
Deox-ribose Suar
Ni!roenous .ase :
/urine : Adenine (uanine /-rimidine : 2-!osine h-mine
/hospha!e
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Nu"$eoti'es of DNA
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*ases !airing*ases !airing
Adenine – Thymine
Guanine – Cytosine
Purines - Pyrimidines
By Hidrogen Bond
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- Denat%re : he !o s!rands of !he DNA helix separa!e or dena!ure
4 Al5ali
4 6ea!
ffec! of al5ali on DNA and 8NA& : DNA s!rands s!a- in!ac!, bu! separa!e&
8NA s!rands are deraded !o nucleo!ides&
$H- *
+ara"teristi" of DNA
$H- *
DNADNA +NA DNA +NA
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- +enat%ration reannealing :
!empera!ure slol- reformin a double helix, iden!ical !o!he oriinal DNA&
+ara"teristi" of DNA
Heat
(ool
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! r i m a r &
! o $ & m
e r i "
S t r u " t
u r e
o f
D NA
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e Se"on'ar& Stru"ture of DNA
.H# D$/0# H#0
13 .wo antiparallel strands for& a right-handed heli)
23 (o&ple&entary base pairing
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a-s of represen!in DNA :
"a% shoin polari!- and base pairin bu! no helical !is!
"b% shoin helical !is! and helix parame!ers bu! no! base pairs
a b
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ways of representing DNA :c showing heli) and base pairs4
d space-filling representation showing &a5or and &inor grooves3
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A do%ble heli)6, , and A for&s of DNA3 .he
solid black lines connect onephosphate gro%p to the ne)t3
DNA heli)
.wist
.wo DNA strand twisted to for& a do%ble heli)
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DNA Replication
prepared ene!ic ma!erial !o reproduc!ion cell di;ision
8eplica!ion ra!e
he eu5ar-o!ic replica!ion ra!e is abou! 10 !imes sloer
!han !he pro5ar-o!ic replica!ion ra!e&
< hours !o replica!e !he human enome
semi conser;a!i;e mechanism
bidirec!ional,
direc!ion of DNA s-n!hesize : => ? 3>
s!ar! a! man- @riin of 8eplica!ion "@8%
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Semi "onseratie
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Schema!ic represen!a!ion of
!he addi!ion of a nucleo!ide !o
a roin s!rand of DNA
durin replica!ion&
S&ntesis a$/a&s goes from ’ to
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Phosphate – O – CH !ase O
"#
H#$#
H H
H H
%# # OH H
Nex! nucleo!ide
ill Boined here
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*i-'ire"tiona$
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Stages in Rep$i"ation !ro"ess
1 (n)ind *mem#u+a, the heli$ :
- .opoisomerase - /ith the aid of DNA "yrase - 0elicase - SS!
% DNA is replicated #y DNA!olymerase - !rimase - DNA !olymerase 222 - 3eadin" and 3a""in" Strand
- 4+aza+i 'ra"ment
Remo5al the RNA primer - DNA !olymerase 2
6 7oint the fra"ment - DNA ly"ase
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3mz&mes re4uire'
on DNA rep$i"ation
1 Topoisomerase : initiation of un)indin" of DNA
% Helicase : accomplishes un)indin" ori"inal dou#le strandDNA
Single-stranded binding protein : sta#ilized sin"le strandDNA as templates to RNA primase and DNA pol
6 Primase : to attaches a small RNA primer
8.DNA Polymerase : proceed alon" sin"le-stranded moleculeof DNA
9 Ligase : or"anize and catalyze formation phosphodiester#ond on the end
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Stru"ture of RNAStru"ture of RNA
Sin"le stranded
RNA nucleotides consist of: 1 Ri#ose *a pentose su"ar )ith 8
car#ons, % !hosphate "roup 4r"anic *nitro"enous, #ases:
- !yrimidines *
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- 2nformation stora"e and transport
*mRNA 5iral RNA,
- 2nfo transfer *tRNA,
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RNA +o'ons
7tart codon : A/8
7top codon : /AA, /A8 and /8A
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#in's of RNA, ma'e b& "e$$
mRNA messen"er RNAis a copy of a "ene carry the information storedin DNA nucleus to cytoplasm *translation machine,
tRNA transfer RNA
as an adaptor to carry aa to appropriate place ascoded #y mRNA
rRNA " ri#osomal RNA
structural component of ri#osomessnRNA small nuclear RNA
in5ol5e in the machinery that process RNAs#et)een nucleus and cytoplasm
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Di&erence 'et(eenDi&erence 'et(een
DNA-RNADNA-RNA
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#$% of RNA in a cell is rRNA&'(% tRNA& (% mRNA
mRNA !as a )-met!ylganosine cap at its (*end and a poly-A tail at its +* end
tRNA forms intrastrand loops containing ,strange,ncleotide ariantstRNA alays !as a +*-//A !ere amino acids areattac!ed
t!e anticodon loop of tRNA binds to t!e codon ofmRNA it!in t!e ribosome introns are remoedfrom t!e primary RNA transcript 0!nRNA1& !ilet!e e2ons remain to ma3e p t!e mRNA
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DNA repair
http://www.mywiseowl.com/articles/Image:Dnarepair1.jpg
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Mismatchrepair
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Base excisionrepair
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Nucleotide excisionrepair
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Double-strand break
repair
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