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<\/p>\n\u2018Bilim insan\u0131\u2019 deyince \u00e7o\u011fumuzun g\u00f6z\u00fcnde laboratuvar\u00adda deneylerine g\u00f6m\u00fclm\u00fc\u015f, ak \u00f6nl\u00fckl\u00fc, g\u00f6zl\u00fckl\u00fc biri canlan\u0131r. Oysa bilimin \u00f6nc\u00fcleri aras\u0131nda \u00e7al\u0131\u015fmas\u0131n\u0131 kum \u00fczerinde (Ar\u015fimet), e\u011fik kulede (Galileo), \u00e7iftlikte (New\u00adton), do\u011fa ara\u015ft\u0131rma gemisinde (Darwin), patent b\u00fcrosunda (Einstein) yapanlar\u0131 biliyoruz. Bilim d\u00fc\u015f\u00fcnsel bir etkinliktir; ye\u00adri laboratuvarla de\u011fil, zek\u00e2, imgelem ve isten\u00e7 g\u00fcc\u00fcyle s\u0131n\u0131rl\u0131d\u0131r. Bunun \u00e7arp\u0131c\u0131 bir \u00f6rne\u011fini \u00e7al\u0131\u015fmalar\u0131n\u0131 aral\u0131ks\u0131z 20 y\u0131l manast\u0131r bah\u00e7esinde s\u00fcrd\u00fcren Ke\u015fi\u015f Mendel vermi\u015ftir.<\/p>\n
Genetik biliminin kurucusu Gregor Mendel, Avusturya \u0130mpa\u00adratorlu\u011fu\u2019na dahil \u00c7ekoslavakya\u2019da yoksul bir k\u00f6yl\u00fc \u00e7ocu\u011fu ola\u00adrak d\u00fcnyaya gelir. O zaman k\u0131rsal kesimde h\u00e2l\u00e2 bir t\u00fcr derebey\u00adlik d\u00fczeni egemendi. Topraks\u0131z k\u00f6yl\u00fcler i\u00e7in bo\u011faz toklu\u011funa \u0131rgatl\u0131k d\u0131\u015f\u0131nda fazla bir se\u00e7enek yoktu; tek kurtulu\u015f yolu belki de e\u011fitimdi. Ne var ki, e\u011fitim de \u00e7o\u011funluk ilkokulla s\u0131n\u0131rl\u0131 kal\u00admaktayd\u0131; daha ilerisi i\u00e7in halk\u0131n parasal g\u00fcc\u00fc yoktu. Herkes gi\u00adbi Gregor\u2019un da do\u011fu\u015ftan al\u0131n yaz\u0131s\u0131 babas\u0131 gibi ren\u00e7ber olmakt\u0131. Ama hay\u0131r, bu \u00e7ocuk d\u00fczenin koydu\u011fu engeli a\u015facak, kendine \u00f6zg\u00fc kararl\u0131l\u0131k i\u00e7inde yetene\u011fini ortaya koyacakt\u0131, ilkokuldaki ba\u015far\u0131s\u0131 g\u00f6z kama\u015ft\u0131r\u0131c\u0131yd\u0131. \u00d6\u011fretmenlerinin \u0131srar\u0131 \u00fczerine aile, sonunda \u00e7ocu\u011fun orta\u00f6\u011frenimi i\u00e7in izin verir. Gregor, evinden uzakta alt\u0131 y\u0131l bir yurtta yetersiz bak\u0131m ve beslenme ko\u015fullar\u0131na g\u00f6\u011f\u00fcs gererek okur; ama, ac\u0131s\u0131n\u0131 uzun y\u0131llar \u00e7ekece\u011fi yorgun, c\u0131l\u0131z ve sa\u011fl\u0131ks\u0131z bir bedenle mezun olur.<\/p>\n
Mendel daha \u00f6\u011frencilik y\u0131llar\u0131nda bilimin b\u00fcy\u00fcs\u00fcne kendi\u00adni kapt\u0131rm\u0131\u015f; \u00f6zellikle botanik yo\u011fun ilgi alan\u0131 olmu\u015ftu. Fakat y\u00fcksek\u00f6\u011frenim onun i\u00e7in ula\u015f\u0131lmas\u0131 g\u00fc\u00e7 bir hayaldi. Burs ola\u00adna\u011f\u0131 yoktu; k\u0131z karde\u015finin ba\u011f\u0131\u015flad\u0131\u011f\u0131 \u00e7eyizi de yeterli olmaktan uzakt\u0131. Mendel i\u00e7in bir tek yol vard\u0131: Bir Katolik manast\u0131r\u0131na gir\u00admek. Avusturya\u2019da botanik m\u00fczesi, bah\u00e7e bitkileri ve zengin ki\u00adtapl\u0131\u011f\u0131yla \u00fcnl\u00fc Br\u00fcnn Manast\u0131r\u0131 Mendel i\u00e7in \u201cideal\u201d bir \u00f6\u011frenim merkeziydi. 25 ya\u015f\u0131nda \u201cpapaz\u201d unvan\u0131n\u0131 alan Mendel\u2019in as\u0131l \u00f6zlemi hi\u00e7 de\u011filse bir ortaokulda \u00f6\u011fretmen olmak, ara\u015ft\u0131rmalar\u0131 i\u00e7in daha elveri\u015fli bir ortam bulmakt\u0131. Bu ama\u00e7la girdi\u011fi s\u0131navda yeterli g\u00f6r\u00fclmez. \u00dcniversite \u00f6\u011freniminden yoksun kalm\u0131\u015f olma\u00ads\u0131 \u00f6nemli bir handikapt\u0131. Gen\u00e7 papaz umudunu yitirmemi\u015ftir. Viyana \u00dcniversitesi\u2019nde d\u00f6rt s\u00f6mestr fizik ve do\u011fal tarih \u00f6\u011fre\u00adnimi g\u00f6rd\u00fckten sonra \u015fans\u0131n\u0131 yeniden dener. Ama yine ba\u015fanl\u0131 g\u00f6r\u00fclmez. S\u0131nav kurulu \u00f6nyarg\u0131l\u0131d\u0131r; kendine \u00f6zg\u00fc de\u011fi\u015fik bir tutum sergileyen genci anlamaktan uzak kal\u0131r. Aday\u0131n \u00f6zellikle evrim ve kal\u0131t\u0131ma ili\u015fkin g\u00f6r\u00fc\u015fleri ba\u011f\u0131\u015flan\u0131r gibi de\u011fildi. Mendel i\u00e7in art\u0131k manast\u0131ra \u00e7ekilip ara\u015ft\u0131rmalar\u0131n\u0131 bah\u00e7e bitkileri \u00fcze\u00adrinde s\u00fcrd\u00fcrmekten ba\u015fka \u00e7are kalmam\u0131\u015ft\u0131.<\/p>\n
Canl\u0131larda \u00f6zelliklerin ku\u015faktan ku\u015fa\u011fa ge\u00e7i\u015fi, Mendel\u2019in s\u00fcrgit ilgi oda\u011f\u0131n\u0131 olu\u015fturan konuydu. Herkes yeni do\u011fan bir yavrunun atalar\u0131n\u0131n \u00f6zelliklerini ta\u015f\u0131d\u0131\u011f\u0131n\u0131 biliyordu. Dahas\u0131, kimi yavru\u00adnun daha \u00e7ok anaya, kimi yavrunun da daha \u00e7ok babaya \u00e7ekti\u011fi g\u00f6zden ka\u00e7m\u0131yordu. Ancak bilinen bu olaylar\u0131n \u201cbilimsel\u201d diye\u00adbilece\u011fimiz bir a\u00e7\u0131klamas\u0131 yoktu ortada. Mendel bezelyeler \u00fcze\u00adrindeki deneylerine \u00f6yle bir a\u00e7\u0131klama bulmak i\u00e7in koyulmu\u015ftu. \u00c7al\u0131\u015fmas\u0131n\u0131, bu ama\u00e7la se\u00e7ti\u011fi 22 \u00e7e\u015fit bezelyenin boylu-bodur, sar\u0131-ye\u015fil, yuvarlak-buru\u015fuk, … gibi 7 \u00e7ift kar\u015f\u0131t \u00f6zellikleri \u00fcze\u00adrinde yo\u011funla\u015ft\u0131r\u0131r. \u00d6rne\u011fin, boylu ve bodur \u00e7e\u015fitlerini \u00e7apraz d\u00f6lledi\u011finde ilk ku\u015fak melez \u00fcr\u00fcn\u00fcn t\u00fcm\u00fcyle boylu oldu\u011funu saptar. Melez \u00fcr\u00fcn\u00fc kendi i\u00e7inde d\u00f6lleyerek elde etti\u011fi ikinci ku\u00ad\u015fak \u00fcr\u00fcn\u00fcn b\u00fcy\u00fck bir b\u00f6l\u00fcm\u00fcn\u00fcn boylu, k\u00fc\u00e7\u00fck bir b\u00f6l\u00fcm\u00fcn\u00fcn ise bodur oldu\u011fu g\u00f6r\u00fcl\u00fcr. (A\u015fa\u011f\u0131daki \u015fekile bak\u0131n\u0131z!) Mendel iki \u00e7e\u015fit aras\u0131ndaki oran\u0131 hesaplar: 1064 bitkinin yakla\u015f\u0131k 3\/4\u2019\u00fc boy\u00adlu, 1\/4\u2019\u00fc bodurdur. \u00d6rneklem b\u00fcy\u00fckl\u00fc\u011f\u00fcnden kaynaklanan olas\u0131 hatay\u0131 g\u00f6z \u00f6n\u00fcne alan Mendel, Oran\u0131 3:1 olarak belirler (Boylu fakt\u00f6r\u00fc B, Bodur fakt\u00f6r\u00fc b ile g\u00f6sterilmi\u015ftir).<\/p>\n
\u015eekilde belirlenen durumun iyi anla\u015f\u0131lmas\u0131 i\u00e7in birka\u00e7 nok\u00adtan\u0131n a\u00e7\u0131kl\u0131k kazanmas\u0131 gerekir: 1) D\u00f6llenmede boylu ve bodur bezelyelerin hangisinin di\u015fi, hangisinin erkek oldu\u011fu, sonucu etkilememektedir. Ba\u015fka bir deyi\u015fle \u00f6zelli\u011fin belirlenmesinde boylu erkek, bodur di\u015fi \u00e7ift ile bodur erkek, boylu di\u015fi \u00e7ifti e\u015f\u00adde\u011ferdir. 2) Di\u015fi ya da erkek her canl\u0131 her \u00f6zellik i\u00e7in biri ba\u015fat, di\u011feri \u00e7ekinik iki fakt\u00f6r ta\u015f\u0131r. Bezelye \u00f6rne\u011finde, ilk ku\u015faktaki Bb melezinde ortaya \u00e7\u0131kan B ba\u015fatt\u0131r, gizli kalan b \u00e7ekiniktir. 3) Di\u015fi ve erkekte her \u00fcreme h\u00fccresi fakt\u00f6rlerden yaln\u0131zca birini ta\u015f\u0131r; \u00f6yle ki, her yavru iki fakt\u00f6rle d\u00fcnyaya gelir. Kuram\u0131n bu temel ilkesine \u201cMendel\u2019in ayr\u0131m yasas\u0131\u201d denmi\u015ftir. 4) \u0130lk ku\u015fak\u00adtaki melez (Bb) yavrular\u0131n t\u00fcm\u00fcyle boylu olmas\u0131, fakt\u00f6rlerin d\u00f6llenmede kayna\u015fmad\u0131\u011f\u0131, ba\u015fat ya da \u00e7ekinik her fakt\u00f6r\u00fcn bireysel kimli\u011fini korudu\u011funu g\u00f6sterir. Nitekim ikinci ku\u015fakta fakt\u00f6rlerin BB, Bb, bB ve bb olarak \u00e7\u0131kt\u0131\u011f\u0131n\u0131 g\u00f6r\u00fcyoruz. \u201cMen\u00addel\u2019in ba\u011f\u0131ms\u0131z \u00e7e\u015fitler\u201d diye bilinen bu yasas\u0131 yavrular\u0131n kimi kez ana ve babaya de\u011fil, ge\u00e7mi\u015fteki atalar\u0131na benzeme olay\u0131n\u0131 da a\u00e7\u0131klamaktad\u0131r. \u015e\u00f6yle ki, ku\u015faktan ku\u015fa\u011fa gizil kalan \u00e7ekinik fakt\u00f6rlerin birbiriyle birle\u015fip ortaya \u00e7\u0131kma olana\u011f\u0131 vard\u0131r. Ayn\u0131 \u015fekilde yavrunun ana-babadan birine daha \u00e7ok benzemesi de ba\u00ad\u015fat ve \u00e7ekinik fakt\u00f6rlerle a\u00e7\u0131klanan bir olayd\u0131r. (Ba\u011f\u0131ms\u0131z \u00e7e\u015fitler yasas\u0131n\u0131 k\u0131saca \u015f\u00f6yle dile getirebiliriz: D\u00f6llenmede iki cinsiyetin her birinden gelen tek fakt\u00f6rler birbiriyle ba\u011f\u0131ms\u0131z ve rasgele birle\u015firler.)<\/p>\n
Mendel ba\u015fka bitkiler \u00fczerinde yapt\u0131\u011f\u0131 deneylerden de ayn\u0131 sonucu alm\u0131\u015ft\u0131r. Daha sonra, biyologlar\u0131n b\u00f6cek, bal\u0131k, ku\u015f ve memeliler \u00fczerinde y\u00fcr\u00fctt\u00fckleri deneyler de onun genetik teo\u00adrisini do\u011frulam\u0131\u015ft\u0131r.<\/p>\n
Mendel teorisi, evrim kuram\u0131n\u0131n ba\u015flang\u0131\u00e7ta a\u00e7\u0131klamas\u0131z b\u0131\u00adrakt\u0131\u011f\u0131 kimi \u00f6nemli noktalara da \u0131\u015f\u0131k tutmu\u015ftur. Evrimi do\u011fal seleksiyonla a\u00e7\u0131klayan Darwin de herkes gibi ana-baba \u00f6zellikle\u00adrinin yavruda bir t\u00fcr kayna\u015ft\u0131\u011f\u0131n\u0131 varsay\u0131yordu. Oysa bu do\u011fru olsayd\u0131, do\u011fal seleksiyonla \u00fcst\u00fcnl\u00fck kazanan \u00f6zelliklerin ku\u015fak\u00adlar boyu zay\u0131flama s\u00fcrecine girmesi gerekirdi. \u00d6rne\u011fin, \u00e7ok h\u0131zl\u0131 ko\u015fan bireyle ko\u015fma h\u0131z\u0131 normal bireyin \u00e7iftle\u015fmesinden do\u011fan bireyin (yavru) ko\u015fma h\u0131z\u0131 ikisi aras\u0131nda olacak, sonraki ku\u015fak\u00ad larda fark daha da azalarak kaybolmaya y\u00fcz tutacakt\u0131r. Darwin de bunun b\u00f6yle olmad\u0131\u011f\u0131n\u0131n fark\u0131ndayd\u0131. Kayna\u015fma varsay\u0131m\u0131 ne kimi yavrular\u0131n ana-babadan yaln\u0131zca birine benzemesi olay\u0131yla, ne de ara s\u0131ra g\u00f6r\u00fcld\u00fc\u011f\u00fc gibi, beklenmedik bir \u00f6zellikle d\u00fcnyaya gelme olay\u0131yla ba\u011fda\u015fmaktayd\u0131. \u00d6zelliklerin \u00f6nceki ku\u015fak veya ku\u015faklardan oldu\u011fu gibi ve ayr\u0131 birimler olarak yavruya ge\u00e7ti\u011fi d\u00fc\u015f\u00fcncesi, Mendel kuram\u0131n\u0131n getirdi\u011fi bir a\u00e7\u0131klamad\u0131r.<\/p>\n
Mendel, kuram\u0131n\u0131 1865\u2019te bilim \u00e7evrelerine sunmu\u015ftu. Ancak Mendel hayatta iken ilgi \u00e7ekmeyen kuram\u0131n \u00f6nemi, 35 y\u0131l son\u00adra kavran\u0131r. Hugo de Vries (1848 – 1935) ve Weismann (1834 – 1914) gibi bilim adamlar\u0131n\u0131n \u00e7al\u0131\u015fmalar\u0131 olmasayd\u0131, Mendel\u2019in devrimsel at\u0131l\u0131m\u0131 belki de daha uzun s\u00fcre g\u00fcn \u0131\u015f\u0131\u011f\u0131na \u00e7\u0131kmaya\u00adcakt\u0131.<\/p>\n
Genetik teorisi, evrim kuram\u0131na yeni bir boyut kazand\u0131rmak\u00adla kalmam\u0131\u015f, g\u00fcn\u00fcm\u00fczde olumlu olumsuz \u00e7ok\u00e7a s\u00f6z\u00fc edilen \u201cgenetik m\u00fchendisli\u011fi\u201d \u00e7al\u0131\u015fmalar\u0131na da yol a\u00e7m\u0131\u015ft\u0131r.<\/p>\n
Kaynak:<\/strong> Cemal Y\u0131ld\u0131r\u0131m, Bilimin \u00d6nc\u00fcleri, Bilim ve Gelecek Kitapl\u0131\u011f\u0131, Kas\u0131m 2007, 24. Bask\u0131, s.143<\/p>\n","protected":false},"excerpt":{"rendered":" \u2018Bilim insan\u0131\u2019 deyince \u00e7o\u011fumuzun g\u00f6z\u00fcnde laboratuvar\u00adda deneylerine g\u00f6m\u00fclm\u00fc\u015f, ak \u00f6nl\u00fckl\u00fc, g\u00f6zl\u00fckl\u00fc biri canlan\u0131r. Oysa bilimin \u00f6nc\u00fcleri aras\u0131nda \u00e7al\u0131\u015fmas\u0131n\u0131 kum \u00fczerinde (Ar\u015fimet), e\u011fik kulede (Galileo), \u00e7iftlikte (New\u00adton), do\u011fa ara\u015ft\u0131rma gemisinde (Darwin), patent b\u00fcrosunda (Einstein) yapanlar\u0131 biliyoruz. Bilim d\u00fc\u015f\u00fcnsel bir etkinliktir; ye\u00adri laboratuvarla de\u011fil, zek\u00e2, imgelem ve isten\u00e7 g\u00fcc\u00fcyle s\u0131n\u0131rl\u0131d\u0131r. Bunun \u00e7arp\u0131c\u0131 bir \u00f6rne\u011fini \u00e7al\u0131\u015fmalar\u0131n\u0131 aral\u0131ks\u0131z 20 […]<\/p>\n","protected":false},"author":429,"featured_media":37349,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[19],"tags":[482,5389,292,5387,5388],"class_list":["post-37348","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-bilim-gundemi","tag-bilim","tag-capraz-dollenme","tag-genetik","tag-johann-gregor-mendel","tag-mendel-teorisi"],"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