{"id":16123,"date":"2016-03-01T12:37:15","date_gmt":"2016-03-01T10:37:15","guid":{"rendered":"http:\/\/109.232.216.219\/~bilimvegelecek\/?p=16123"},"modified":"2018-01-08T12:41:18","modified_gmt":"2018-01-08T09:41:18","slug":"enformasyon-arkeye-metabolizma-gercek-bakteriye-mi-ceker","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2016\/03\/01\/enformasyon-arkeye-metabolizma-gercek-bakteriye-mi-ceker","title":{"rendered":"Enformasyon arkeye metabolizma ger\u00e7ek bakteriye mi \u00e7eker?"},"content":{"rendered":"

Yeni \u00e7al\u0131\u015fmalar g\u00f6steriyor ki, arke k\u00f6kenli insan (\u00f6karyot) genleri, kabaca bilgi ak\u0131\u015f\u0131 temelli diyebilece\u011fimiz s\u00fcre\u00e7lere, yani DNA e\u015flenmesi, mRNA sentezi ve i\u015flenmesi ve protein sentezinin devasa dinami\u011fine ili\u015fkinler. Ger\u00e7ek bakteri k\u00f6kenli genler ise metabolik yollar\u0131n i\u015flemesine ili\u015fkinler. <\/em><\/p>\n

\u00d6karyotlar, ger\u00e7ek bakteriler ve arkeler diye, tek bir varsay\u0131msal k\u00f6ke ba\u011flanan \u00fc\u00e7 ana canl\u0131 grubu yerine, son yap\u0131lan genom \u00e7al\u0131\u015fmalar\u0131 \u0131\u015f\u0131\u011f\u0131nda k\u00f6ken itibar\u0131yla canl\u0131l\u0131\u011f\u0131n temel grup say\u0131s\u0131n\u0131n ikiye indirgendi\u011finden ge\u00e7en ayki yaz\u0131m\u0131zda s\u00f6z etmi\u015ftik. \u00d6karyotlar\u0131n arkelerin bir karde\u015f grubu oldu\u011funa ve ger\u00e7ek bakterilerle yap\u0131lan endosimbiyoz ili\u015fkilerinin ya\u015fam\u0131n evriminin son 2 milyar y\u0131ll\u0131k \u00e7ok h\u00fccreli yap\u0131s\u0131n\u0131n mihenk ta\u015flar\u0131n\u0131 olu\u015fturdu\u011funa da k\u0131saca de\u011finmi\u015ftik. Son be\u015f y\u0131l i\u00e7indeki genom \u00e7apl\u0131 konuya ili\u015fkin ara\u015ft\u0131rmalar\u0131 b\u00fcnyesine katan ve an\u0131lan \u00fc\u00e7 ya\u015fam formunun pek \u00e7ok temsilcisinin genom d\u00fczeyinde protein ve ribozomal RNA varyasyonunu ele alan kapsaml\u0131 \u00e7al\u0131\u015fman\u0131n sonucu olarak ortaya konan filogenetik topolojinin, bu iki k\u00f6kl\u00fc ve \u00f6karyotlar\u0131n arkelerin i\u00e7inden \u00e7\u0131kan karde\u015f bir grup oldu\u011funu net bi\u00e7imde g\u00f6sterdi\u011fini de s\u00f6ylemi\u015ftik.1<\/sup><\/p>\n

\u0130nsan\u0131n kendine bi\u00e7ti\u011fi \u2018ulvi\u2019 rol\u00fcn anlams\u0131zl\u0131\u011f\u0131<\/strong><\/p>\n

Bu gezegenin \u00fc\u00e7 milyar y\u0131l \u00f6ncesinden daha geriye uzanmas\u0131 muhtemel derin tarihsel ortakl\u0131\u011f\u0131n insan\u0131n kendine bakmas\u0131ndaki belki de en sars\u0131c\u0131 ve muazzam taraf\u0131, Do\u011fu Afrika\u2019n\u0131n g\u00f6rece sessiz ve bar\u0131\u015f\u00e7\u0131l ortam\u0131n\u0131, Rif Vadisi\u2019nin son 1,5 milyon y\u0131l i\u00e7inde ge\u00e7irdi\u011fi de\u011fi\u015fimlerden kendi an\u0131 hasebinde pay\u0131n\u0131 alan Homo sapiens<\/em>\u2019in ge\u00e7ti\u011fimiz 100 bin sene i\u00e7inde adeta terk ederek gezegene yay\u0131lmas\u0131n\u0131n son birka\u00e7 bin y\u0131l\u0131nda kendine bi\u00e7ti\u011fi tarihsel-ulvi rol\u00fcn anlams\u0131zl\u0131\u011f\u0131d\u0131r.<\/p>\n

Be\u015feri tarih, e\u011fer Braudel\u2019in izinden gidersek, co\u011frafyan\u0131n imkanlar\u0131 dahilinde okundu\u011funda b\u00fcy\u00fck heyecan veren bir k\u00fclt\u00fcr ve kayna\u015fma tarihidir elbet.2<\/sup> Ancak son 250 senenin Avrupa siyasal co\u011frafyas\u0131n\u0131n herc\u00fcmerc\u00fc i\u00e7inde zihinlere kaz\u0131nan mitsel bir ayr\u0131ks\u0131l\u0131k-benzersizlik ve tarihsizlik fikrine kap\u0131larak okundu\u011funda ise3<\/sup>, nice masum kan\u0131 ak\u0131tan, insan\u0131n akl\u0131n\u0131n trajik bir yan\u0131lsamas\u0131na ortakl\u0131ktan \u00f6teye ge\u00e7ilmeyecektir ku\u015fkusuz.<\/p>\n

Sonu\u00e7ta prokaryotik iki ya\u015fam formunun \u00fcr\u00fcn\u00fc olarak bu gezegende y\u00fcz binlerce k\u00f6kenda\u015f\u0131 ile uzun bir evrimsel tarihi payla\u015farak ya\u015fayan insan\u0131 s\u00f6zde kusursuz ve b\u00f6l\u00fcnemez varl\u0131k y\u0131ld\u0131z\u0131 olarak kutsayan do\u011fal teolojinin tarihsel olarak anla\u015f\u0131l\u0131r temsilcilerinin4<\/sup> g\u00fcn\u00fcm\u00fczdeki mirasyedileri olan \u201cyarat\u0131l\u0131\u015f\u00e7\u0131lar\u0131n\u201d ya da \u201cak\u0131ll\u0131 tasar\u0131m\u201dc\u0131lar\u0131n paleontolojik ya da biyokimyasal laf salatalar\u0131 ise, Marx\u2019\u0131n Hegel\u2019i tamamlad\u0131\u011f\u0131 vurgu ile s\u00f6ylersek5<\/sup>, g\u00fcn\u00fcm\u00fcz evrimsel biyoloji bilgisinin konuya ili\u015fkin k\u0131s\u0131mlar\u0131 yan\u0131nda olsa olsa tutars\u0131z bir s\u00fcreklilik arz eden farslardan ibarettir.<\/p>\n

Arke k\u00f6kenli genler hayati<\/strong><\/p>\n

Yeniden konumuzun asli \u00e7er\u00e7evesine d\u00f6nersek, ge\u00e7ti\u011fimiz ayki yaz\u0131m\u0131zda, insan ya da herhangi bir \u00f6karyot genomuna bakt\u0131\u011f\u0131m\u0131zda, i\u00e7erilen arke ve \u00f6bakteri k\u00f6kenli genler i\u00e7in \u015fu sorular\u0131 sormu\u015ftuk:<\/p>\n

1) Tipik \u00f6karyotik hayat\u0131n son 2 milyar y\u0131lda ortaya \u00e7\u0131kan genetik yenilikleri kar\u015f\u0131s\u0131nda, insan ya da herhangi bir \u00f6karyot genomundaki arke ve ger\u00e7ek bakteri genlerinin ifade dereceleri ve yayg\u0131nl\u0131klar\u0131, do\u011fal se\u00e7ilimle bi\u00e7imlenmi\u015flikleri a\u00e7\u0131s\u0131ndan durum nedir?<\/p>\n

2) \u00d6karyotlardaki hangi prokaryot genetik miras\u0131 daha hayatidir, protein sentezi arkeye enerji metabolizmas\u0131 ger\u00e7ek bakteriye mi \u00e7eker?<\/p>\n

Bu sorulardan ilki, \u00f6karyot genomundaki arke ve ger\u00e7ek bakteri genlerinin i\u015flevsel kar\u015f\u0131l\u0131klar\u0131n\u0131 da ifade eden evrimle\u015fmelerine ili\u015fkindir ve sorunun yan\u0131t\u0131 olabilecek bilgileri veren insan genomu taramas\u0131 esasl\u0131 bir \u00e7al\u0131\u015fmay\u0131 burada \u00f6zetleyelim: David Alvarez-Ponce and James O. McInerney adl\u0131 ara\u015ft\u0131r\u0131c\u0131lar\u0131n ger\u00e7ekle\u015ftirdi\u011fi, insan genomuna odaklanm\u0131\u015f bu \u00e7al\u0131\u015fma konumuz a\u00e7\u0131s\u0131ndan son derece \u00f6nemli noktalar\u0131 net bir bi\u00e7imde vurguluyor.6<\/sup> \u00d6ncelikle, insan genomundaki arke k\u00f6kenli genlerin ger\u00e7ek bakteri k\u00f6kenli genlere oranla do\u011fal se\u00e7ilimle bi\u00e7imlenme d\u00fczeylerinin daha y\u00fcksek oldu\u011funu g\u00f6r\u00fcyoruz. Arke k\u00f6kenli genlerin i\u015flevsel yayg\u0131nl\u0131\u011f\u0131na ve \u00f6nemine i\u015faret eden \u00e7arp\u0131c\u0131 bir bulgu bu. Yine, genlerin ifade d\u00fczeyleri ve dokulardaki ifade yayg\u0131nl\u0131klar\u0131na bakt\u0131\u011f\u0131m\u0131zda da insan genomunda arke genleri \u00f6nde g\u00f6r\u00fcn\u00fcyor. \u00c7al\u0131\u015fman\u0131n, modern genetik ve genomik ba\u011flam\u0131nda \u00e7ok \u00f6nemli oldu\u011funu d\u00fc\u015f\u00fcnebilece\u011fimiz bir di\u011fer sonucu da, arke k\u00f6kenli genlerin, protein-protein etkile\u015fim a\u011flar\u0131nda daha merkezi ve kontrol mahiyetli i\u015flevlerinin bulunmas\u0131. Gen etkile\u015fiminin yayg\u0131nl\u0131\u011f\u0131 a\u00e7\u0131s\u0131ndan ve \u00e7oklu genli biyolojik \u00f6zellik evrimi \u00e7er\u00e7evesinde b\u00fcy\u00fck \u00f6nemi bulunan protein etkile\u015fimlerinin a\u011f\u0131rl\u0131\u011f\u0131 da arkeden yana g\u00f6z\u00fck\u00fcyor. Geni tekil, di\u011fer genlerden ve geni\u015f manas\u0131yla gen etkile\u015fim \u00e7evresinden ve organizman\u0131n ve pop\u00fclasyonun tarihinden ba\u011f\u0131ms\u0131z g\u00f6ren \u201cgen bencilci\u201d indirgemecili\u011fin ideologlar\u0131na prokaryotik bir yan\u0131t m\u00fctevaz\u0131 bir \u015fekilde dil \u00e7\u0131kar\u0131yor adeta.<\/p>\n

\u0130kinci sorumuzun yan\u0131t\u0131 yine ayn\u0131 ara\u015ft\u0131r\u0131c\u0131lar\u0131n di\u011fer bulgular\u0131nda yer al\u0131yor: \u00c7al\u0131\u015fman\u0131n ikinci b\u00f6l\u00fcm\u00fcnde, insan genomunda saptanan arke ve ger\u00e7ek bakteri genlerinin e\u015flenikleri genetik model olarak kullan\u0131lan bildi\u011fimiz farede susturulmu\u015flar. Bu gen susturmalar\u0131 yap\u0131ld\u0131\u011f\u0131nda en \u00e7ok \u00f6l\u00fcmle sonu\u00e7lanan etki yaratan genler de yine arke genleri. Arke k\u00f6kenli genlerin son derece hayati oldu\u011funu s\u00f6ylemek art\u0131k hayli m\u00fcmk\u00fcn.<\/p>\n

Peki, arke ve ger\u00e7ek bakteri k\u00f6kenli genlerin nitelikleri a\u00e7\u0131s\u0131ndan, yani biyolojik s\u00fcre\u00e7lerin hangilerinde i\u015f g\u00f6rd\u00fckleri bak\u0131m\u0131ndan ne s\u00f6yleyebiliriz? \u00c7al\u0131\u015fma g\u00f6steriyor ki, arke k\u00f6kenli insan (\u00f6karyot) genleri, kabaca bilgi ak\u0131\u015f\u0131 temelli diyebilece\u011fimiz s\u00fcre\u00e7lere, yani DNA e\u015flenmesi, mRNA sentezi ve i\u015flenmesi ve protein sentezinin devasa dinami\u011fine ili\u015fkinler. Ger\u00e7ek bakteri k\u00f6kenli genler ise metabolik yollar\u0131n i\u015flemesine ili\u015fkinler.<\/p>\n

Hemen s\u00f6yleyelim, bu sonu\u00e7lar\u0131n benzerlerine bu \u00e7al\u0131\u015fmadan k\u0131sa s\u00fcre \u00f6ncesinde ger\u00e7ekle\u015ftirilen bira mayas\u0131 (tek h\u00fccreli, koloni \u015feklinde birlik olu\u015fturabilen bir \u00f6karyot) ara\u015ft\u0131rmas\u0131nda da ula\u015f\u0131lm\u0131\u015f durumda.7<\/sup> Yine, ge\u00e7ti\u011fimiz y\u0131l yay\u0131nlanan iki do\u011frudan insan h\u00fccre k\u00fclt\u00fcr\u00fc \u00e7al\u0131\u015fmas\u0131 da, insan genomundaki kadim genetik miras s\u00f6z konusu oldu\u011funda, a\u015fa\u011f\u0131 yukar\u0131 ayn\u0131 sonu\u00e7lara ula\u015fm\u0131\u015f durumda.8,9<\/sup><\/p>\n

***<\/p>\n

Ya\u015fam\u0131n derin k\u00f6klerinden \u00f6karyotlara ve bir \u00f6karyot olan insana gelen prokaryotik mirasa ili\u015fkin son d\u00f6nem \u00e7al\u0131\u015fmalar\u0131n\u0131 bir nebze \u00f6zetlemeye \u00e7al\u0131\u015ft\u0131k. Bug\u00fcn h\u00fccre ve bile\u015fenleri ve t\u00fcm organizman\u0131n kendisi, modernitenin ilk d\u00f6nem materyalistlerinden de La Mettrie\u2019nin basit makinesi ya da William Paley\u2019in saat gibi i\u015fleyen ve ilahi kudretin par\u0131lt\u0131s\u0131n\u0131 aksettiren cihaz\u0131 olmaktan \u00e7ok \u00f6tede ve onlardan hayli ayr\u0131ks\u0131 olarak, tarihsel ge\u00e7mi\u015flerinin t\u00fcm safhalar\u0131n\u0131 yans\u0131tt\u0131\u011f\u0131n\u0131 evrimsel biyolojinin cihazlar\u0131yla anlamaya devam etti\u011fimiz biyolojik \u00e7e\u015fitlili\u011fin ba\u011flant\u0131lar\u0131 olarak kar\u015f\u0131m\u0131zda duruyor.<\/p>\n

H\u00fccre ve organizman\u0131n derin evrimselli\u011fine ili\u015fkin bu ba\u015f d\u00f6nd\u00fcr\u00fcc\u00fc geli\u015fmelerin dayand\u0131\u011f\u0131 ara\u015ft\u0131rma gelene\u011fi, tan\u0131msal h\u00fccrebiliminin ba\u011fnazl\u0131\u011f\u0131 i\u00e7inde sesi k\u0131s\u0131lmas\u0131na kar\u015f\u0131n m\u00fccadele g\u00fcc\u00fcn\u00fc yitirmeyen modern sentez d\u00f6neminin ayr\u0131ks\u0131, devrimci h\u00fccrebilimcisi Cyril Darlington\u2019un b\u00fcy\u00fck eserinde10<\/sup> bile \u00f6ng\u00f6remedi\u011fi ama ayn\u0131 ruhu devam ettiren bir k\u00f6kten kavray\u0131\u015f ile canl\u0131 ve canl\u0131l\u0131\u011fa bak\u0131\u015f\u0131m\u0131z\u0131 derinden etkilemeye devam edece\u011fe benziyor.<\/p>\n

Kaynaklar<\/strong><\/p>\n

1) Lionel Guy, Jimmy H. Saw ve Thijs J.G. Ettema, Archaeal legacy of Eukaryotes: A phylogenomic perspective, Cold Spring Harb. Perspect. Biol<\/em>., 2014; 6:a016022.<\/p>\n

2) Fernand Braudel, The Mediterranean and the Mediterranean World in the Age of Philip II<\/em>, Collins, 1971.<\/p>\n

3) Eric Hobsbawm, Milletler ve Milliyet\u00e7ilik<\/em> (\u00c7ev. Osman Ak\u0131nhay), Ayr\u0131nt\u0131 Yay\u0131nlar\u0131, 2014.<\/p>\n

4) William Paley, Natural Theology or Evidence of the Existence and Attributes of the Deity, collected from the appearances of nature<\/em>, 1802 (Oxford University Press, 2014).<\/p>\n

5) Karl Marx, Louis Bonaparte\u2019\u0131n On Sekiz Brumaire\u2019i<\/em> (\u00c7ev. Tan\u0131l Bora), \u0130leti\u015fim Yay\u0131nlar\u0131, 2010.<\/p>\n

6) David Alvarez-Ponce ve James O. McInerney, The Human Genome Retains Relics of Its Prokaryotic Ancestry: Human Genes of Archaebacterial and Eubacterial Origin Exhibit Remarkable Differences, Genome Biology and Evolution, 2011, 3:782-790.<\/p>\n

7) J.A. Cotton ve J.O. McInerney, Eukaryotic genes of archaebacterial origin are more important than the more numerous eubacterial genes, irrespective of function, 2010, Proc Natl Acad. Sci. U S A, 107:17252\u201317255.<\/p>\n

8) Tim Wang, K\u0131van\u00e7 Birsoy, Nicholas W. Hughes, Kevin M. Krupczak, Yorick Post, Jenny J. Wei, Eric S. Lander ve David M. Sabatini, Identification and characterization of essential genes in the human genome, Science<\/em>, 350: 1096-1101.<\/p>\n

9) Vincent A. Blomen1, Peter M\u00e1jek2, Lucas T. Jae, Johannes W. Bigenzahn, Joppe Nieuwenhuis, Jacqueline Staring, Roberto Sacco, Ferdy R. van Diemen, Nadine Olk, Alexey Stukalov, Caleb Marceau, Hans Janssen, Jan E. Carette, Keiryn L. Bennett, Jacques Colinge, Giulio Superti-Furga ve Thijn R. Brummelkamp, Gene essentiality and synthetic lethality in haploid human cells, Science, 350: 1092-1096.<\/p>\n

10) C.D. Darlington, Recent Advances in Cytology<\/em>, J. & A. Churchill, 1932.<\/p>\n","protected":false},"excerpt":{"rendered":"

Yeni \u00e7al\u0131\u015fmalar g\u00f6steriyor ki, arke k\u00f6kenli insan (\u00f6karyot) genleri, kabaca bilgi ak\u0131\u015f\u0131 temelli diyebilece\u011fimiz s\u00fcre\u00e7lere, yani DNA e\u015flenmesi, mRNA sentezi ve i\u015flenmesi ve protein sentezinin devasa dinami\u011fine ili\u015fkinler. Ger\u00e7ek bakteri k\u00f6kenli genler ise metabolik yollar\u0131n i\u015flemesine ili\u015fkinler. \u00d6karyotlar, ger\u00e7ek bakteriler ve arkeler diye, tek bir varsay\u0131msal k\u00f6ke ba\u011flanan \u00fc\u00e7 ana canl\u0131 grubu yerine, son yap\u0131lan […]<\/p>\n","protected":false},"author":67,"featured_media":16124,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[182,21,32,231],"tags":[493,200,431,497,1088,1893],"class_list":["post-16123","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-145-sayi","category-biyoloji","category-evrim","category-molekuler-biyoloji-ve-genetik","tag-bakteri","tag-evrim","tag-gen","tag-homo-sapiens","tag-metabolizma","tag-mrna"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t