Genetika kel 15

CLONAL SELECTION

Up to this point, we have avoided the question o how an o!"anis# initiates the s$nthesis o 

anti%odies spe&ii& to anti"ens that it has not p!eviosl$ en&ounte!ed' This is ni&el$ e(plained

 %$ the &lonal sele&tion theo!$' )e&all that all the anti%odies p!odu&ed %$ a sin"le *

l$#pho&$te have the sa#e anti"en %indin" spe&ii&it$' *ut die!ent &ells in a population o *

l$#pho&$tes will have unde!"one die!ent "eno#e !ea!!an"e#ents leadin" to the p!odu&tion

o anti%odies with die!ent spe&ii&ities' Thus, the population o * l$#pho&$tes in a hu#an

o! a #ouse will %e p!odu&in" a ve!$ la!"e va!iet$ o anti%odies' The &lonal sele&tion theo!$

states that the %indin" o a pa!ti&ula! o!ei"n anti"en to an anti%od$ on the su!a&e o a *

l$#pho&$te sti#ulates that &ell to divide, p!odu&in" la!"e nu#%e!s o this pa!ti&ula! *

l$#pho&$te +a &lone- o identi&al &ell. and thus la!"e a#ounts o the pa!ti&ula! anti%od$ that

!e&o"ni/es the o!ei"n anti"en +i"' 10'11.

i" 10'11

S&e#ati& dia"!a# o the !ole o &lonal sele&tion in the i##une !esponse' Geno#i&

!ea!!an"e#ents, the use o alte!nate 2oinin" sites, and so#ati& h$pe!#utation all &ont!i%ute to

the develop#ent o a population o * l$#pho&$tes that &olle&tivell$ p!odu&e a vast va!iet$ o 

die!ent anti%odies +althou"ht ea&h &ell p!odu&es onl$ a sin"le t$pe o anti%od$.' 3hen a

 pa!ti&ula! anti%od$ %inds to an anti"en, the &ell p!odu&in" that pa!ti&ula! anti%od$ is

sti#ulated to divide' Ate! a se!ies o &ell divisions, a &lonal population o * &els is p!odu&ed,

with all &ell p!odu&in" the sa#e anti%od$'

T)ANSLATE

Sa#pai saat ini, ka#i #en"hinda!i pe!tan$aan tentan" %a"ai#ana suatu o!"anis#e #e#ulai

sintesis anti%odi spesiik te!hadap anti"en $an" %elu# p!eviosl$ dite#ui' Ini %aik di2elaskan

oleh teo!i seleksi klonal' In"at %ahwa se#ua anti%odi $an" dihasilkan oleh li#osit * tun""al

#e#iliki kekhususan #en"ikat anti"en $an" sa#a' Tapi sel $an" %e!%eda dala# populasi

li#osit * akan #en"ala#i pen$usunan ulan" "eno# $an" %e!%eda #en$e%a%kan p!oduksi

anti%odi den"an kekhususan $an" %e!%eda' 4en"an de#ikian, populasi li#osit * pada

#anusia atau tikus akan #e#p!oduksi %e!%a"ai san"at %esa! da!i anti%odi' Teo!i seleksi

klonal #en$atakan %ahwa pen"ikatan anti"en asin" te!tentu pada anti%odi pada pe!#ukaan

li#osit * #e!an"san" %ahwa sel #e#%elah, #en"hasilkan se2u#lah %esa! * ini li#osit

 

te!tentu +a &lone da!i sel identik. dan 2u#lah sehin""a %esa! anti%odi te!tentu $an"

#en"akui anti"en asin" +"%!' 10'11.'''

Ga#%a! 10'11

Ske#a dia"!a# pe!an seleksi klonal dala# !espon i#un' 6en$usunan ulan" "eno#,

 pen""unaan situs %e!"a%un" alte!nati, dan h$pe!#utation so#atik se#ua %e!kont!i%usi

te!hadap pe!ke#%an"an populasi li#osit * $an" se&a!a kolekti #en"hasilkan %e!%a"ai

#a&a# anti%odi $an" %e!%eda +#eskipun setiap sel han$a #en"hasilkan satu 2enis anti%odi.'

7etika anti%odi te!tentu #en"ikat anti"en, sel $an" #e#p!oduksi anti%odi $an" te!tentu

di!an"san" untuk #e#%a"i' Setelah se!an"kaian pe#%elahan sel, populasi klonal sel *

dip!oduksi, den"an se#ua sel $an" #e#p!oduksi anti%odi $an" sa#a'