{"id":12336,"date":"2014-12-01T00:28:16","date_gmt":"2014-11-30T22:28:16","guid":{"rendered":"http:\/\/109.232.216.219\/~bilimvegelecek\/?p=12336"},"modified":"2018-04-19T15:55:11","modified_gmt":"2018-04-19T12:55:11","slug":"milyar-yil-suren-evrim-laboratuvarda-60-gunde-gerceklestirildi-tekhucrelilerden-cokhucrelilere","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2014\/12\/01\/milyar-yil-suren-evrim-laboratuvarda-60-gunde-gerceklestirildi-tekhucrelilerden-cokhucrelilere","title":{"rendered":"Milyar y\u0131l s\u00fcren evrim laboratuvarda 60 g\u00fcnde ger\u00e7ekle\u015ftirildi: Tekh\u00fccrelilerden \u00e7okh\u00fccrelilere"},"content":{"rendered":"

Ba\u015flarda tekh\u00fccreliler vard\u0131. Bug\u00fcnse, milyonlarca y\u0131l sonra, bitkiler, hayvanlar, mantar ve algler bir\u00e7ok h\u00fccrenin tek bir yap\u0131 gibi birlikte \u00e7al\u0131\u015fmas\u0131ndan olu\u015fuyor. Peki bu h\u00fccreler nas\u0131l tek ba\u015f\u0131na ya\u015farlarken di\u011fer h\u00fccrelerle i\u015fbirli\u011fi yapmaya ve birbirine ba\u011fl\u0131 tek bir \u00fcnite gibi \u00e7al\u0131\u015fmaya ba\u015flad\u0131lar?<\/p>\n

Bilim d\u00fcnyas\u0131 evrimsel ge\u00e7i\u015fte en b\u00fcy\u00fck ad\u0131m\u0131n \u00e7okh\u00fccreli organizmalar\u0131n tekh\u00fccrelilerden evrilmesi oldu\u011fu konusunda hemfikir. \u00c7\u00fcnk\u00fc \u00e7okh\u00fccrelili\u011fin ortaya \u00e7\u0131k\u0131\u015f\u0131, d\u00fcnyadaki ya\u015fam\u0131 de\u011fi\u015ftirecek bir evrimdir. \u00c7okh\u00fccrelilerin boyutunun b\u00fcy\u00fck olmas\u0131na ek olarak, \u00e7okh\u00fccrelilik biyolojik karma\u015f\u0131kl\u0131\u011f\u0131 yeni biyolojik yap\u0131lar\u0131n olu\u015fmas\u0131 ile art\u0131rm\u0131\u015ft\u0131r. En ay\u0131rt edici evrimsel soru, \u00e7okh\u00fccrelili\u011fin ba\u015flang\u0131\u00e7 noktas\u0131 ve s\u00fcrd\u00fcrebilirli\u011finin nas\u0131l sa\u011fland\u0131\u011f\u0131d\u0131r. Bu ge\u00e7i\u015fin anla\u015f\u0131lmas\u0131n\u0131 zor k\u0131lan etmenlerden biri, ge\u00e7i\u015f formlar\u0131n\u0131n soyunun t\u00fckenmi\u015f olmas\u0131 ve ge\u00e7i\u015fin fizyolojisi, ekolojisi ve evrimsel s\u00fcreci hakk\u0131nda bilgimizin az olmas\u0131d\u0131r.<\/p>\n

Tekh\u00fccreli canl\u0131lardan \u00e7okh\u00fccreli canl\u0131lara evrimsel ge\u00e7i\u015fin ilk kan\u0131t\u0131 3-3,5 milyar y\u0131l \u00f6ncesine ait h\u00fccre farkl\u0131la\u015fmas\u0131 g\u00f6steren prokaryot, ipliksi ve k\u00fcme olu\u015fturan siyanobakteri benzeri organizmalar\u0131n fosillerinden geliyor. \u00c7okh\u00fccreli \u00f6karyotlar\u0131n ise 1 milyar y\u0131l \u00f6nce var olduklar\u0131 d\u00fc\u015f\u00fcn\u00fcl\u00fcyor. Tarihin kendini tekrarlamas\u0131 gibi, \u00e7okh\u00fccreli organizmalar birbirinden ba\u011f\u0131ms\u0131z olarak en az 25 kere tekh\u00fccreli atalar\u0131ndan evrilmi\u015f. Bu evrili\u015f h\u00e2l\u00e2 devam ediyor, hatta bazen bu s\u00fcre\u00e7 tersine de i\u015fliyor. Bu ge\u00e7i\u015f hakk\u0131ndaki bilgilerimiz yeterli say\u0131da olmasa da, ana a\u015famalar\u0131 ve \u00e7okh\u00fccreli organizasyon i\u00e7in gerekli olan ko\u015fullar biliniyordu. H\u00fccre tutunumu, h\u00fccre ileti\u015fimi ve koordinasyonu bunlardan birka\u00e7\u0131. Bu \u00e7okh\u00fccrelilik i\u00e7in gerekli olan \u00f6zellikler tekh\u00fccreli organizmalarda da g\u00f6zlemleniyordu. Dolay\u0131s\u0131yla, tekh\u00fccreli organizmalardan \u00e7okh\u00fccreli organizmalara ge\u00e7i\u015fin bilimsel anlamda kolay olaca\u011f\u0131 s\u00f6ylenebilinir.<\/p>\n

Almanya, Pl\u00f6n\u2019deki Max Planck Evrimsel Biyoloji Enstit\u00fcs\u00fc ile birlikte Yeni Zelanda ve Amerika\u2019daki ara\u015ft\u0131rmac\u0131lar, ana a\u015famalar\u0131n \u00e7ok k\u0131sa s\u00fcrede ger\u00e7ekle\u015fti\u011fini deneysel evrimi kullanarak g\u00f6steriyor. Bu deneyi ger\u00e7ekle\u015ftirirken, tekh\u00fccreli maya h\u00fccrelerini (Saccharomyces cerevisiae<\/em>) kullanarak \u00e7okh\u00fccrelili\u011fin se\u00e7ilimi i\u00e7in yer\u00e7ekiminden yararland\u0131lar. \u00d6nce tekh\u00fccreliler basit k\u00fcmeler olu\u015fturuyor, sonras\u0131nda grupla\u015fm\u0131\u015f h\u00fccreler s\u0131v\u0131 i\u00e7ersinde tek kalm\u0131\u015f h\u00fccrelere oranla daha \u00e7abuk bir \u015fekilde \u00e7\u00f6kmeye ba\u015fl\u0131yor. Bu \u015fekilde, \u00e7\u00f6kelen h\u00fccre k\u00fcmesinden bir miktar yeni h\u00fccre se\u00e7ilip yeni s\u0131v\u0131 ortam\u0131na aktar\u0131ld\u0131\u011f\u0131nda, s\u00fcrekli daha b\u00fcy\u00fck veya birbirlerine tutunmu\u015f h\u00fccre k\u00fcmeleri i\u00e7eren yap\u0131lar se\u00e7ilmi\u015f oluyor. Ara\u015ft\u0131rmac\u0131lar bu i\u015flemi 10 farkl\u0131 deney t\u00fcp\u00fc i\u00e7in tekrarlad\u0131 ve sadece 60 g\u00fcn s\u00fcren transferin sonunda 10 deney t\u00fcp\u00fcn\u00fcn her birinde tek bir yap\u0131n\u0131n se\u00e7ilim sonunda bask\u0131n bi\u00e7im oldu\u011funu g\u00f6zlemlediler. Kar tanesi \u015feklinde olu\u015fan k\u00fcme h\u00fccreleri \u015eekil\u2019de g\u00f6r\u00fclebilir.<\/p>\n

Bu g\u00f6zlemin sonucunda olu\u015fan sorulardan birisi \u00e7okh\u00fccreli k\u00fcmelenmenin s\u0131v\u0131 ortam\u0131ndaki farkl\u0131 h\u00fccrelerin biraraya gelip tutunmalar\u0131 yoluyla m\u0131, h\u00fccrelerin b\u00f6l\u00fcnmesi s\u0131ras\u0131nda yavru h\u00fccrelerin anne h\u00fccrelere tutunup ayr\u0131lmamas\u0131 yoluyla m\u0131 meydana geldi\u011fiydi. Ara\u015ft\u0131rmalar ikinci hipotezin do\u011frulu\u011funu ispatlad\u0131. Bir di\u011fer soru ise, olu\u015fan basit \u00e7okh\u00fccreli yap\u0131n\u0131n nas\u0131l \u00e7o\u011fald\u0131\u011f\u0131yd\u0131. Bunun, olu\u015fan k\u00fc\u00e7\u00fck kar tanesi yap\u0131s\u0131n\u0131n ancak kendi ebeveyninin boyutuna ula\u015ft\u0131ktan sonra, b\u00fcy\u00fck kar tanesi yap\u0131s\u0131ndan ayr\u0131lmas\u0131 ile ger\u00e7ekle\u015fti\u011fi g\u00f6zlemlendi. \u0130lgili videoya derginin internet sayfas\u0131ndan (http:\/\/kisalt.com\/a1v) ula\u015fabilirsiniz.<\/p>\n

Ara\u015ft\u0131rmac\u0131lar ayn\u0131 zamanda, kar tanelerinin birbirinden ayr\u0131ld\u0131\u011f\u0131 noktalarda belirli h\u00fccrelerin \u00f6ld\u00fc\u011f\u00fcn\u00fc g\u00f6zlemlemi\u015fler. Bu da, \u00e7okh\u00fccrelilik tan\u0131m\u0131 i\u00e7in ge\u00e7erli olan \u00f6zelliklerden farkl\u0131la\u015fman\u0131n ve i\u015fb\u00f6l\u00fcm\u00fcn\u00fcn, en basit formunda 60 g\u00fcnl\u00fck deney sonucunda se\u00e7ilimini g\u00f6steriyor. Deneyi daha uzun s\u00fcre devam ettirdiklerinde, kar tanesi yap\u0131lar\u0131n\u0131n bi\u00e7imlerinin daha d\u00fczenli ve k\u00fcre bi\u00e7imli yap\u0131lara evrildikleri de g\u00f6sterilmi\u015f.<\/p>\n

Bu deneyin sonu\u00e7lar\u0131 ve \u00e7okh\u00fccrelili\u011fin evrimle\u015fme bi\u00e7imi \u00fczerine yap\u0131lm\u0131\u015f olan baz\u0131 g\u00f6zlemler, baz\u0131 teorik beklentilerin aksine, \u00e7okh\u00fccrelili\u011fe evrili\u015fin b\u00fcy\u00fck \u00e7apta genomik karma\u015f\u0131kl\u0131k gerektirmedi\u011fini ispatl\u0131yor.<\/p>\n

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

    \n
  1. Ratcliff, W. C., R. F. Denison, M. Borrello, and M. Travisano; \u201cExperimental Evolution of Multicellularity\u201d, Proceedings of the National Academy of Sciences<\/em>, 109.5 (2012): 1595-600.<\/li>\n
  2. Grosberg, Richard K., and Richard R. Strathmann; \u201cThe Evolution of Multicellularity: A Minor Major Transition?\u201d, Annual Review of Ecology, Evolution, and Systematics<\/em>, 38.1 (2007): 621-54.<\/li>\n
  3. \u201cFrom Single Cells to Multicellular Life: Researchers Capture the Emergence of Multicellular Life in Real-time Experiments.\u201d, ScienceDaily, 19 Nov. 2014. <http:\/\/www.sciencedaily.com\/releases\/2014\/11\/141106113334.htm><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    Ba\u015flarda tekh\u00fccreliler vard\u0131. Bug\u00fcnse, milyonlarca y\u0131l sonra, bitkiler, hayvanlar, mantar ve algler bir\u00e7ok h\u00fccrenin tek bir yap\u0131 gibi birlikte \u00e7al\u0131\u015fmas\u0131ndan olu\u015fuyor. Peki bu h\u00fccreler nas\u0131l tek ba\u015f\u0131na ya\u015farlarken di\u011fer h\u00fccrelerle i\u015fbirli\u011fi yapmaya ve birbirine ba\u011fl\u0131 tek bir \u00fcnite gibi \u00e7al\u0131\u015fmaya ba\u015flad\u0131lar? Bilim d\u00fcnyas\u0131 evrimsel ge\u00e7i\u015fte en b\u00fcy\u00fck ad\u0131m\u0131n \u00e7okh\u00fccreli organizmalar\u0131n tekh\u00fccrelilerden evrilmesi oldu\u011fu konusunda hemfikir. […]<\/p>\n","protected":false},"author":862,"featured_media":23739,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[167,19,21],"tags":[200,718],"class_list":["post-12336","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-130-sayi","category-bilim-gundemi","category-biyoloji","tag-evrim","tag-evrimsel-biyoloji"],"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