{"id":14828,"date":"2016-09-01T13:22:13","date_gmt":"2016-09-01T10:22:13","guid":{"rendered":"http:\/\/109.232.216.219\/~bilimvegelecek\/?p=14828"},"modified":"2017-12-20T13:23:37","modified_gmt":"2017-12-20T10:23:37","slug":"darwin-devrimi-6-genombilim-ve-turlesme-darwin-ispinozlari","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2016\/09\/01\/darwin-devrimi-6-genombilim-ve-turlesme-darwin-ispinozlari","title":{"rendered":"Darwin devrimi – 6\u00a0Genombilim ve t\u00fcrle\u015fme: Darwin ispinozlar\u0131"},"content":{"rendered":"

Bulunan gen, gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc ve bu b\u00fcy\u00fckl\u00fckle ili\u015fkili beslenme varyasyonu a\u00e7\u0131s\u0131ndan, Darwin ispinozlar\u0131n\u0131n t\u00fcrle\u015fme hatt\u0131ndaki belirgin bir yol ayr\u0131m\u0131na denk gelen bir farkl\u0131la\u015fmaya i\u015faret etti\u011finden, ekolojik parametrelerin de\u011fi\u015fmesiyle yeni t\u00fcrlerin nas\u0131l ortaya \u00e7\u0131kabilece\u011fine de \u0131\u015f\u0131k tutuyor. <\/em><\/p>\n

T\u00fcr olarak tan\u0131mlanan s\u0131n\u0131fland\u0131rma kategorisi dahilindeki genetik \u00e7e\u015fitlilik temeline oturtulan biyolojik \u00f6zellik \u00e7e\u015fitlili\u011finin zaman ve mekandaki da\u011f\u0131l\u0131m\u0131n\u0131 bi\u00e7imlendiren de\u011fi\u015fim s\u00fcre\u00e7lerinin ba\u015fl\u0131cas\u0131na do\u011fal se\u00e7ilimle evrimle\u015fme ya da Darwinci evrim dendi\u011fini, do\u011fal se\u00e7ilimle evrimle\u015fme s\u00fcrecinin kabul\u00fcn\u00fcn yaratt\u0131\u011f\u0131 bilimsel devrimin ise Darwin devrimi \u015feklinde vurguland\u0131\u011f\u0131n\u0131 ge\u00e7en yaz\u0131lar\u0131m\u0131zda belirtmi\u015ftik. Tarihsel bir bilim olan evrimsel biyolojinin tarihine ili\u015fkin yapt\u0131\u011f\u0131m\u0131z bu \u00e7ok genel \u00f6zeti tamamlayaca\u011f\u0131m\u0131z yaz\u0131m\u0131z\u0131n son iki b\u00f6l\u00fcm\u00fcnde, t\u00fcr-i\u00e7i ve t\u00fcrler-aras\u0131 genetik varyasyon saptama \u00e7al\u0131\u015fmalar\u0131n\u0131n nihai d\u00fczeyi olan ve evrimsel biyolojik sorunlara b\u00fcy\u00fck a\u00e7\u0131kl\u0131k getiren genom \u00e7apl\u0131 genetik varyasyon analizleri temelinde, do\u011fal se\u00e7ilimin etkin oldu\u011fu bir s\u00fcre\u00e7 olarak, yeni t\u00fcr olu\u015fumlar\u0131n\u0131n izlerini iki pop\u00fcler model evrimsel organizmaya odaklanarak s\u00fcrece\u011fiz.<\/p>\n

\u0130spinoz sava\u015flar\u0131<\/strong><\/p>\n

Genom d\u00fczeyindeki genetik varyasyonu hedef alan, yani bir t\u00fcr\u00fcn b\u00fct\u00fcn kromozomlar\u0131ndaki genetik bilgiyi pop\u00fclasyonlar\u0131n farkl\u0131la\u015fmas\u0131 ve t\u00fcrle\u015fmesi bahsinde anlamland\u0131rmaya odaklanan ilk \u00f6rne\u011fimiz, Charles Darwin\u2019in me\u015fhur Galapagos Adalar\u0131nda g\u00f6zlemledi\u011fi ve onu yak\u0131n benzerlikleri \u00fczerinden t\u00fcrlerin sabit olmad\u0131\u011f\u0131 fikrine g\u00f6t\u00fcren ispinozlar\u0131 konu ediniyor.<\/p>\n

\"\"
Darwin ispinozlar\u0131n\u0131n John Gould taraf\u0131ndan yap\u0131lm\u0131\u015f \u00e7izimleri.<\/figcaption><\/figure>\n

Latin Amerika \u00fclkesi Ekvator\u2019un 1000 km kadar a\u00e7\u0131klar\u0131nda yer alan Galapagos Adalar\u0131ndaki ispinozlar, onlar \u00fczerine ilk evrimsel ve ekolojik \u00e7al\u0131\u015fmay\u0131 yapan David Lack\u2019\u0131n tabiriyle \u201cDarwin \u0130spinozlar\u0131\u201d (1), \u00a0do\u011fal se\u00e7ilimle evrimle\u015fmenin, g\u00f6rece\u011fimiz gibi insan \u00f6mr\u00fcn\u00fcn k\u0131sa bir diliminde dahi g\u00f6zlemlenebilecek parlak bir \u00f6rne\u011fini sunarlar. Lack\u2019\u0131n miras\u0131n\u0131 devralan ve 40 y\u0131l\u0131 a\u015fk\u0131n s\u00fcredir Galapagos Adalar\u0131nda ispinozlar\u0131 evrimsel biyoloji ve ekolojinin t\u00fcm kuramsal ve pratik ara\u00e7lar\u0131 e\u015fli\u011finde irdeleyen Grant\u2019lerin de belirtti\u011fi gibi, Darwin ispinozlar\u0131, tek bir atasal t\u00fcrden k\u00f6ken alan yak\u0131ndan benzer 15 kadar t\u00fcr\u00fcn adalar\u0131n ekolojik farkl\u0131l\u0131klar\u0131 ve d\u00f6nemsel sert \u00e7evresel de\u011fi\u015fimler izd\u00fc\u015f\u00fcm\u00fcnde \u00e7e\u015fitlendi\u011fi evrimsel bir panoraman\u0131n par\u00e7alar\u0131d\u0131rlar. (2)<\/p>\n

\u0130spinozlardaki gaga \u015fekli ve b\u00fcy\u00fckl\u00fc\u011f\u00fc, v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fc ile ili\u015fkili olmalar\u0131n\u0131n yan\u0131 s\u0131ra, besin bollu\u011fu ve \u00e7e\u015fidi ile t\u00fcr-i\u00e7i \/ t\u00fcrler-aras\u0131 rekabet aras\u0131ndaki ili\u015fkinin de \u00f6nemli g\u00f6stergeleridir. (2)<\/p>\n

\"\"
G. magnirostris.<\/figcaption><\/figure>\n

Ele alaca\u011f\u0131m\u0131z genom \u00e7al\u0131\u015fmas\u0131nda, Galapagos sistemindeki k\u00fc\u00e7\u00fck bir ada olan Daphne Major\u2019de 2004-2005 y\u0131llar\u0131 aras\u0131nda meydana gelen sert kurakl\u0131k esnas\u0131nda ger\u00e7ekle\u015fen besin k\u0131tl\u0131\u011f\u0131 kar\u015f\u0131s\u0131nda, adadaki orta v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fcne sahip ve b\u00fcy\u00fck gagal\u0131 yer ispinozu Geospiza fortis<\/em>\u2019in yine ayn\u0131 adadaki b\u00fcy\u00fck v\u00fccutlu yer ispinozu Geospiza magnirostris<\/em> ile olan d\u00fc\u015f\u00fck rekabet ba\u015far\u0131s\u0131 nedeniyle, gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc a\u00e7\u0131s\u0131ndan ge\u00e7irdi\u011fi evrimsel farkl\u0131la\u015fma inceleniyor.<\/p>\n

Tarihlerinin bir par\u00e7as\u0131 olarak co\u011frafi a\u00e7\u0131dan kesi\u015fen t\u00fcrlerin, kaynaklar k\u0131s\u0131tl\u0131 oldu\u011funda aralar\u0131nda ortaya \u00e7\u0131kan rekabet sonucunda biyolojik \u00f6zelliklerinin farkl\u0131la\u015fmas\u0131 Darwin\u2019den bu yana vurgulanan bir hadisedir. Ayn\u0131 biyolojik \u00f6zelli\u011fin farkl\u0131 bi\u00e7imlerinden birinin di\u011ferinin yerine ge\u00e7mesi \u015feklinde ortaya \u00e7\u0131kan ve rekabetin \u015fiddetini de d\u00fc\u015f\u00fcren bu farkl\u0131la\u015fmalar t\u00fcrle\u015fme s\u00fcrecinin de \u00f6nemli bir bile\u015fenidirler.<\/p>\n

\u0130nceleyece\u011fimiz ispinoz genomlar\u0131 \u00e7al\u0131\u015fmas\u0131 da, Daphne Major\u2019daki yukarda an\u0131lan kurakl\u0131k esnas\u0131nda, G.fortis<\/em>\u2019in b\u00fcy\u00fck gagal\u0131 formlar\u0131n\u0131n di\u011fer t\u00fcrle (G.magnirostris<\/em>) olan rekabet sonucunda elenmesi ve G.fortis<\/em>\u2019in g\u00f6rece k\u00fc\u00e7\u00fck gagal\u0131 formlar\u0131n\u0131n kurakl\u0131ktan b\u00f6ylece sa\u011f \u00e7\u0131kmas\u0131n\u0131n dayand\u0131\u011f\u0131 genetik temele odaklanmakta. (3)<\/p>\n

\u00c7al\u0131\u015fman\u0131n ilk aya\u011f\u0131nda, Daphne Major\u2019daki iki t\u00fcr dahil, toplam 6 ispinoz t\u00fcr\u00fcn\u00fcn genom dizileri her t\u00fcre ait bireyler kullan\u0131larak \u00e7\u0131kar\u0131lm\u0131\u015f. Se\u00e7ilen bu alt\u0131 t\u00fcr, a\u011fa\u00e7ta ve zeminde ya\u015fayanlar \u015feklinde ve b\u00fcy\u00fck, orta ve k\u00fc\u00e7\u00fck v\u00fccutlu olmalar\u0131 temelinde, Darwin ispinozlar\u0131n\u0131n ekolojik ayr\u0131mla\u015fmalar\u0131n\u0131 b\u00fcy\u00fck oranda temsil eden bir \u00e7er\u00e7evede \u00a0grupland\u0131r\u0131lm\u0131\u015flar. V\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fc esas al\u0131narak grupland\u0131r\u0131lan bu alt\u0131 t\u00fcr\u00fcn evrimsel tarihindeki genetik d\u00f6n\u00fcm noktalar\u0131n\u0131n bu grupland\u0131rma dahilindeki resminin \u00e7\u0131kar\u0131lmas\u0131 ama\u00e7lanm\u0131\u015f b\u00f6ylece.<\/p>\n

HMAG2 geni<\/strong><\/p>\n

Genom dizileri kar\u015f\u0131la\u015ft\u0131r\u0131ld\u0131\u011f\u0131nda, alt\u0131 t\u00fcr\u00fcn tamam\u0131nda da y\u00fcksek farkl\u0131la\u015fma g\u00f6steren 7 genom b\u00f6lgesi saptanm\u0131\u015f. Bu b\u00f6lgeler a\u00e7\u0131s\u0131ndan yap\u0131lan v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fc esasl\u0131 grup kar\u015f\u0131la\u015ft\u0131rmalar\u0131nda ise b\u00f6lgelerden birinin \u00f6zellikle y\u00fcksek farkl\u0131l\u0131k g\u00f6sterdi\u011fi ortaya \u00e7\u0131kmakta. Bu b\u00f6lge dahilinde yer alan ve genomdaki pek \u00e7ok genin proteine d\u00f6n\u00fc\u015fme s\u00fcrecini kontrol eden di\u011fer genler \u00fczerine etkili bir gen olan HMGA2 ise \u00f6zellikle \u00f6n plana \u00e7\u0131kmakta.<\/p>\n

Bu genin faredeki e\u015fleni\u011findeki keskin bir mutasyonun c\u00fcce fareler yaratt\u0131\u011f\u0131, insandaki e\u015fleni\u011finin boy uzunlu\u011fu, kafatas\u0131-y\u00fcz boyutu bile\u015fenlerinin konumlanmas\u0131yla ili\u015fkili bulundu\u011funa dikkati \u00e7eken ara\u015ft\u0131r\u0131c\u0131lar, bir sonraki a\u015famada genin ispinozlardaki gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc ili\u015fkisi \u00fczerine yo\u011funla\u015f\u0131yorlar.<\/p>\n

\u00d6ncelikle, HMAG2 geninin birbirinden farkl\u0131 iki temel varyant\u0131 oldu\u011fu saptanm\u0131\u015f ve bu varyantlar\u0131 do\u011furan evrimsel hadisenin, \u00e7al\u0131\u015fmadaki 6 t\u00fcr\u00fcn dahil oldu\u011fu ve di\u011fer ispinozlar\u0131 da i\u00e7eren evrimsel a\u011fa\u00e7ta b\u00fcy\u00fck ve k\u00fc\u00e7\u00fck v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fc yol ayr\u0131m\u0131na denk geldi\u011fi g\u00f6steriliyor.<\/p>\n

\u00c7al\u0131\u015fman\u0131n as\u0131l \u00e7arp\u0131c\u0131 sonucu ise, kendi i\u00e7indeki farkl\u0131la\u015fmas\u0131n\u0131n b\u00fcy\u00fck oranda ifade de\u011fi\u015fimi yaratan varyantlara yol a\u00e7t\u0131\u011f\u0131, yeni proteinler do\u011furmad\u0131\u011f\u0131 anla\u015f\u0131lan bu HMAG2 geninin v\u00fccut b\u00fcy\u00fckl\u00fc\u011f\u00fcnden ziyade, gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc ile ili\u015fkili olmas\u0131. Genin b\u00fcy\u00fck gagal\u0131larda sadece belli bir formu, k\u00fc\u00e7\u00fck gagal\u0131larda ise di\u011fer bir formu yer al\u0131yor. Gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc a\u00e7\u0131s\u0131ndan de\u011fi\u015fkenlik g\u00f6steren (hem k\u00fc\u00e7\u00fck hem de b\u00fcy\u00fck gagal\u0131lar i\u00e7eren) pop\u00fclasyonlarda ise genin her iki formu da belli s\u0131kl\u0131klarda yer al\u0131yorlar.<\/p>\n

\u00c7al\u0131\u015fman\u0131n hedef aya\u011f\u0131 ise, Daphne Major\u2019deki 2004-2005\u2019te ger\u00e7ekle\u015fen sert kurakl\u0131k esnas\u0131nda meydana gelen besin k\u0131tl\u0131\u011f\u0131n\u0131n yaratt\u0131\u011f\u0131, G.fortis<\/em> ve G.magnirostris<\/em> aras\u0131ndaki rekabetin, G.fortis<\/em>\u2019teki b\u00fcy\u00fck gagal\u0131lar\u0131n elenmesine yol a\u00e7mas\u0131n\u0131n HMAG2 ile ili\u015fkisini \u00e7\u00f6z\u00fcmlemeye y\u00f6nelik. Uzun s\u00f6z\u00fcn k\u0131sas\u0131, kurakl\u0131k esnas\u0131ndaki besin k\u0131tl\u0131\u011f\u0131n\u0131n G.fortis<\/em>\u2019in b\u00fcy\u00fck gagal\u0131 formlar\u0131nda (dolay\u0131s\u0131yla b\u00fcy\u00fck gagal\u0131l\u0131kla ili\u015fkili HMAG2 formlar\u0131nda) yaratt\u0131\u011f\u0131 elenmenin (negatif do\u011fal se\u00e7ilimin) s = 0,59 gibi olduk\u00e7a y\u00fcksek bir de\u011ferle meydana geldi\u011fini ifade ediliyor.<\/p>\n

Sonu\u00e7 olarak bu genom d\u00fczeyli \u00e7al\u0131\u015fma, t\u00fcrler aras\u0131 rekabetin yaratt\u0131\u011f\u0131 t\u00fcr i\u00e7i do\u011fal se\u00e7ilimle ili\u015fkili \u00f6nemli bir aday geni ortaya \u00e7\u0131karm\u0131\u015f durumda. Bu gen, gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc ve bu b\u00fcy\u00fckl\u00fckle ili\u015fkili beslenme varyasyonu a\u00e7\u0131s\u0131ndan, Darwin ispinozlar\u0131n\u0131n t\u00fcrle\u015fme hatt\u0131ndaki belirgin bir yol ayr\u0131m\u0131na denk gelen bir farkl\u0131la\u015fmaya i\u015faret etti\u011finden, ekolojik parametrelerin de\u011fi\u015fmesiyle yeni t\u00fcrlerin nas\u0131l ortaya \u00e7\u0131kabilece\u011fine de \u0131\u015f\u0131k tutuyor. Bir ba\u015fka deyi\u015fle do\u011fal se\u00e7ilimin yeni t\u00fcrlerin olu\u015fumunu te\u015fvik edebilmesinin genom seviyesinden g\u00f6sterildi\u011fi parlak bir \u00f6rne\u011fini sunuyor.<\/p>\n

\u00d6n\u00fcm\u00fczdeki ay, Cichlid bal\u0131klardan benzer bir \u00f6rne\u011fe odaklanarak tart\u0131\u015fmam\u0131za son noktay\u0131 koymu\u015f olaca\u011f\u0131z.<\/p>\n

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

1) David Lack, Darwin\u2019s Finches<\/em>, Cambridge University Press, 1947.<\/p>\n

2) Peter R. Grant ve B. Rosemary Grant, How and Why Species Multiply: The Radiation of Darwin\u2019s Finches<\/em>, Princeton University Press, 2008.<\/p>\n

3) Sangeet Lamichhaney, Fan Han, Jonas Berglund, Chao Wang, Markus S\u00e4llman Alm\u00e9n, Matthew T. Webster, B. Rosemary Grant, Peter R. Grant, Leif Andersson. A beak size locus in Darwin\u2019s finches facilitated character displacement during a drought, Science<\/em>, 352: 470-474, 2016.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Bulunan gen, gaga b\u00fcy\u00fckl\u00fc\u011f\u00fc ve bu b\u00fcy\u00fckl\u00fckle ili\u015fkili beslenme varyasyonu a\u00e7\u0131s\u0131ndan, Darwin ispinozlar\u0131n\u0131n t\u00fcrle\u015fme hatt\u0131ndaki belirgin bir yol ayr\u0131m\u0131na denk gelen bir farkl\u0131la\u015fmaya i\u015faret etti\u011finden, ekolojik parametrelerin de\u011fi\u015fmesiyle yeni t\u00fcrlerin nas\u0131l ortaya \u00e7\u0131kabilece\u011fine de \u0131\u015f\u0131k tutuyor. T\u00fcr olarak tan\u0131mlanan s\u0131n\u0131fland\u0131rma kategorisi dahilindeki genetik \u00e7e\u015fitlilik temeline oturtulan biyolojik \u00f6zellik \u00e7e\u015fitlili\u011finin zaman ve mekandaki da\u011f\u0131l\u0131m\u0131n\u0131 bi\u00e7imlendiren de\u011fi\u015fim […]<\/p>\n","protected":false},"author":67,"featured_media":14831,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[188,1475,21,32],"tags":[461,200,431,661,1691],"class_list":["post-14828","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-151-sayi","category-bilim-ve-tarih","category-biyoloji","category-evrim","tag-darwin","tag-evrim","tag-gen","tag-kuslar","tag-turlesme"],"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