kuliah 5-6. genetika mikroflora mulut

7/26/2019 Kuliah 5-6. Genetika Mikroflora Mulut

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Mikrobiologi Mulut

Prof. Dr. Dwi Suryanto

drg. Lisna Unita, M.Kes.


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Kuliah 5-6. Genetika Mikroflora Mulut


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The genetics of oral microorganism as an

area of study is still very much in its infancy. Genetic analysis of the oral microbiota only

began in earnest in 1!" #ith the first re$ort

of the $resence of $lasmid %&' in strain of

Streptococcusmutans. The genoty$e of a microbial stain is the total

com$lement of genetic information that is

carried by the strain on the chromosomal($lasmid( or viral %&' molecules that

com$rise its total genome.


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)&' usually consists of a single

$olynucleotide chain. %&'( on the other hand( consists of t#o

$olynucleotide chains. The t#o %&' chains( or strands( are oriented

in o$$osite directions and held together byhydrogen bonds bet#een the nitrogenous

bases on o$$osite strands.

%&' dan )&'


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*ecause of their si+es( sha$es( and

arrangement of $olar grou$s( the %&' bases

form com$lementary $airs.

'denine $airs #ith thymine ,t#o hydrogenbonds and cytosine $airs #ith guanine ,three

hydrogen bonds.


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DNA and RNA


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T/ G)0/23

1. Ma4or Groove

. Minor Groove

1 /78 9 1: *'2/ ,"; ':

1 *'2/ %72T'&


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DNA NUCLEOTIDA

RNA NUCLEOTIDA


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Basa Nitrogen

Pyrimidine nucleotides

Purinenucleotides


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G/&0M( 2 %&'


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1. &/G'T7/?


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2ince the t#o strands of %&' are only linkedby the non-covalent forces( they can easily be

se$arated in the laboratory( for eFam$les by

increasing tem$erature or high $.

2e$aration of the t#o %&' strands( a $rocesskno#n as denaturation( is readily reversible.

)educing the tem$erature( or the $( #ill

allo# hydrogen bonds bet#een

com$lementary %&' seuences to reform ,re-

annealing.


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1.


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%&'

%&'

)&'

=oly$e$tides


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%&' )e$lication

7n $rinci$le( co$ying %&'-- a $rocess called %&'re$lication -- is very sim$le. The t#o

com$lementary %&' strands se$arate( and

because each nucleotide can only $air #ith its

com$lement-- adenine #ith thymine and cytosine

#ith guanine -- each strand can be used as a

tem$late to build a ne# com$lementary strand(

$roducing t#o %&' molecules.


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%&' re$lication starts and then $roceeds in bothdirections until the original %&' molecule is

com$letely re$licated.


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DNA Re"li#ation

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$ene !%"ression


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Transcri$tion

&'e "ortion of t'e DNA t'at is trans#ribed

into an RNA ole#ule is #alled a

trans#ri"tion unit. An en(ye #alled RNA

"olyerase #arries out trans#ri"tion. )it'

t'e 'el" of "rotein trans#ri"tion fa#tors, itatta#'es to t'e beginning of a region of t'e

DNA #alled t'e "rooter, "ries t'e DNA

strands a"art, and untwists a s'ort "ortion

of t'e double 'eli%.


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&ranskri"si


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Translation

Translation3 The synthesis of a $oly$e$tideusing the genetic information encoded in an

m)&' molecule. There is a change of

IlanguageI from nucleotides to amino acids.

7n translation( a cell reads an m)&' messageand assembles a $oly$e$tide accordingly.


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$eneti# *odes$eneti# *odes


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Proses &ranslasi


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&erinasi &ranslasi


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%&' can be acuired by either vertical or

hori+ontal. ertical transmission refers to the transfer of

a co$y of the $arental %&' to daughter cells

u$on cell division. ori+ontal transmission refers to the

acuisition of foreign %&'( #hich can occur

bet#een clones of the same s$ecies or

related and even diverse s$ecies.


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Transformation( in #hich a cell takes u$ isolated

%&' molecules from the medium surrounding itJ


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7t #as in 1 that Ared Griffith( #orking #ith

$neumococcus ,Streptococcus pneumoniae(

discovered that avirulent strains could be restored tovirulence by incubation #ith an eFtract from killed

virulent cells.

&ransforation


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2iFteen years later( 'very( Maceod and Mc


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There are four ty$es of transformation #hich arein many #ays uite distinct3 natural com$etence(

induced com$etence( $roto$last transformation(

and electro$oration.


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&ransforation


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The com$etent cell are able to take u$ linier

double-stranded %&',such as the fragments

$roduced #hen chromosomal %&' is liberated

from a bacterial cell. 7n order for this %&' to be re$licated and

inherited it must undergo recombination #ith a

homologous region of the reci$ient

chromosome.


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'lthough some organisms are able to take u$

totally unrelated %&'( the absence of

homology $revents recombination occurringJ

the %&' taken u$ is therefore degraded and

lost. This $rocess is therefore limited to

introduction of %&' from closely related

organisms( usually different genetically

marked strains of the same s$ecies.


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*on+ugation


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2everal genera of Gram-$ositive bacteria $ossess

reasonably #ell-characteri+ed con4ugation system3

Streptomycesand Enterococcus faecalis.


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*on+ugatie "ilus


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Me#'anis of "lasid DNA transfer by #on+ugation


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Transduction

Transduction involves $hage-mediated transfer of

genetic material. This $rocess is normally highly s$ecific for $hage

%&'. Bith some $hages( errors can be made and

fragments of bacterial %&' are occasionally

$ackaged by mistake( leading to $hage-like $articles

that contain a segment of bacterial genome.


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/vidence of genetic eFchange by

transduction among oral microorganims is

limited.

*acterio$hage have been detected inanumber of oral microorganisms.


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)eferensi

Marsh % =( Martin M. ::. 0ral Microbiology.


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kuliah 5-6. genetika mikroflora mulut

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