{"id":9787,"date":"2021-02-09T19:46:09","date_gmt":"2021-02-09T16:46:09","guid":{"rendered":"http:\/\/blog.ulubat.org\/?p=9787"},"modified":"2021-05-21T09:52:51","modified_gmt":"2021-05-21T06:52:51","slug":"tek-yumurta-ikizleri-gercekten-ikiz-mi","status":"publish","type":"post","link":"https:\/\/blog.ulubat.org\/index.php\/genel\/tek-yumurta-ikizleri-gercekten-ikiz-mi\/","title":{"rendered":"TEK YUMURTA \u0130K\u0130ZLER\u0130 GER\u00c7EKTEN \u2018\u0130K\u0130Z\u2019 M\u0130?"},"content":{"rendered":"\n

Genetik alan\u0131nda yap\u0131lan, \u00f6zellikle de \u00e7evresel fakt\u00f6rlerin ve genetik kodun birbirlerini nas\u0131l etkiledi\u011fi ve birlikte ki\u015finin hayat\u0131n\u0131 nas\u0131l \u015fekillendirdi\u011fi \u00fczerine yap\u0131lan ara\u015ft\u0131rmalarda bir\u00e7ok kez tek yumurta ikizlerinden gelen verilerden yararlan\u0131lm\u0131\u015ft\u0131r. Ancak bu \u00e7al\u0131\u015fmalarda sahip olduklar\u0131 \u00f6neme ra\u011fmen, bu ki\u015filerin genomik farkl\u0131l\u0131klar\u0131 hakk\u0131nda \u00e7ok fazla bilinmeyen nokta bulunmaktad\u0131r. Johnsson v.d., Ocak 2021 Nature Genetics<\/em>\u2019te yay\u0131mlanan makaleleriyle bu duruma daha yak\u0131ndan bakmay\u0131 ve bilinmeden varsay\u0131lan noktalar\u0131 ayd\u0131nlatmay\u0131 ama\u00e7lam\u0131\u015ft\u0131r. Bu ayki yaz\u0131mda, onlar\u0131n \u00e7al\u0131\u015fmalar\u0131ndan ve bu ara\u015ft\u0131rma \u00fczerine yap\u0131lan ba\u015fka incelemelerden, r\u00f6portajlardan yola \u00e7\u0131karak monozigot ikizlerin belki de yeni fark edilmi\u015f olan genetik farkl\u0131l\u0131klar\u0131na dair birka\u00e7 bilgi payla\u015fmay\u0131 ama\u00e7l\u0131yorum.<\/p>\n\n\n\n

\"\"
https:\/\/metronorth.health.qld.gov.au\/news\/third-type-of-twin<\/a><\/figcaption><\/figure>\n\n\n\n

Monozigot ikizlerin t\u00fcm genetik materyal a\u00e7\u0131s\u0131ndan da \u2018ikiz\u2019 olduklar\u0131 alg\u0131s\u0131na ra\u011fmen asl\u0131nda bu bireyler DNA\u2019lar\u0131nda farkl\u0131l\u0131klar ta\u015f\u0131yabilmektedir. Bu farkl\u0131l\u0131klar, bazen zigot a\u015famas\u0131 sonras\u0131nda ya\u015fanan mekanizmalarla a\u00e7\u0131klanabilmektedir (Kratz vd., 2014). Ancak tek yumurta ikizleri aras\u0131nda bulunan ortalama genetik farkl\u0131l\u0131k say\u0131s\u0131, bu farkl\u0131l\u0131klara yol a\u00e7an mutasyon tipi ve zamanlamalar\u0131 hala tam olarak bilinmemektedir (Jonsson vd., 2021). deCODE \u015firketinde bu ara\u015ft\u0131rmay\u0131 y\u00fcr\u00fcten bilim insanlar\u0131; bu genetik farkl\u0131l\u0131klar\u0131 daha iyi anlayabilmek, inceleyebilmek i\u00e7in \u00e7al\u0131\u015fm\u0131\u015flar ve ikizlerin anne karn\u0131nda birka\u00e7 varyasyon elde ettiklerini dolay\u0131s\u0131yla do\u011fum s\u0131ras\u0131nda bile birbirlerinden genetik olarak farkl\u0131 olduklar\u0131n\u0131 bildirmi\u015flerdir (Offord, 2021). \u0130ncelenen 381 tek yumurta ikizi \u00e7ifti aras\u0131nda 38\u2019i genetik olarak birbirlerinin t\u0131pat\u0131p ayn\u0131s\u0131 olsalar da ikizlerden \u00e7o\u011fu -muhtemelen geli\u015fim d\u00f6neminin erken evrelerinde ortaya \u00e7\u0131kan- farkl\u0131l\u0131klara sahiptir (Saey, 2021). Bu mutasyonlar\u0131, olu\u015ftuklar\u0131 zaman dilimini ve ne ifade ettiklerini anlayabilmek i\u00e7in ara\u015ft\u0131rma grubu bir\u00e7ok dal\u0131 ve a\u015famas\u0131 bulunan bir genetik dizileme s\u00fcrecini izlemi\u015ftir. \u00c7al\u0131\u015fmada yer alan bilim insanlar\u0131ndan K\u00e1ri Stef\u00e1nsson, g\u00f6zlemledikleri ilgi \u00e7ekici bir durumdan daha bahsetmi\u015ftir. Analizlere g\u00f6re baz\u0131 durumlarda ikizlerden biri bir mutasyonu her h\u00fccresinde ta\u015f\u0131rken di\u011feri hi\u00e7bir h\u00fccresinde bulundurmayabilir. Ayn\u0131 ba\u011flamda ikizlerden biri h\u00fccrelerinin sadece bir k\u0131sm\u0131nda belli bir mutasyona sahip olan h\u00fccreler bulundururken di\u011ferinin t\u00fcm h\u00fccrelerinde bu mutasyon g\u00f6zlemlenebilmektedir. Stef\u00e1nsson ve tak\u0131m arkada\u015flar\u0131n\u0131n ortaya koydu\u011fu bulgu, ilk defa bu \u015fekilde g\u00f6sterilebilmi\u015ftir (Offord, 2021). <\/p>\n\n\n\n

\"\"
https:\/\/labmedicineblog.com\/2016\/01\/04\/chromosome-structure-staining-and-naming\/<\/a><\/figcaption><\/figure>\n\n\n\n

Peki bu bulgular genel olarak ne ifade ediyor olabilir? Yak\u0131n zamana kadar tek yumurta ikizleri aras\u0131ndaki genetik farkl\u0131l\u0131klar\u0131n \u00e7evresel fakt\u00f6rlerden kaynakland\u0131\u011f\u0131 d\u00fc\u015f\u00fcn\u00fclmekteydi. Ancak bu ara\u015ft\u0131rmadaki gibi \u00e7\u0131kt\u0131lar ile yava\u015f yava\u015f g\u00f6r\u00fcyoruz ki asl\u0131nda bu ki\u015filer aras\u0131nda anne karn\u0131ndan beri var olan farkl\u0131l\u0131klar bulunabilmektedir. Jonsson v.d.\u2019nin \u00e7al\u0131\u015fmas\u0131ndan \u00f6nce ger\u00e7ekle\u015ftirilmi\u015f bir ba\u015fka \u015fa\u015f\u0131rt\u0131c\u0131 sonu\u00e7lar ortaya koyan \u00e7al\u0131\u015fma da Carl Bruder taraf\u0131ndan y\u00fcr\u00fct\u00fclm\u00fc\u015ft\u00fcr. Burada 19 tek yumurta ikizi \u00e7iftinin genomlar\u0131n\u0131 inceleyen ara\u015ft\u0131rma ekibi, kromozomlar\u0131n baz\u0131 noktalar\u0131nda ikizlerin farkl\u0131 dizilere sahip oldu\u011funu g\u00f6zlemlemi\u015ftir. Bu farkl\u0131l\u0131klar\u0131n en ilgin\u00e7lerinden biri, ikizlerden birinde l\u00f6semi riskini art\u0131rd\u0131\u011f\u0131 d\u00fc\u015f\u00fcn\u00fclen genlerden biri g\u00f6r\u00fclm\u00fc\u015fken ve bu ki\u015fi ger\u00e7ekten de l\u00f6semi hastas\u0131yken di\u011fer ikizin bu durumdan etkilenmemi\u015f olmas\u0131d\u0131r\u00a0(Casselman, 2008).\u00a0<\/p>\n\n\n\n

Yaz\u0131n\u0131n ba\u015f\u0131nda da belirtti\u011fim gibi ikizlerden elde edilen genetik veriler \u015fimdiye kadar y\u00fcr\u00fct\u00fclen ve literat\u00fcre ge\u00e7en bir\u00e7ok ara\u015ft\u0131rmada \u00f6nemli bir rol oynam\u0131\u015ft\u0131r. Stef\u00e1nsson,\u00a0The Scientist\u00a0<\/em>dergisi ile yapt\u0131\u011f\u0131 r\u00f6portajda ara\u015ft\u0131rma grubunun ortaya koydu\u011fu bulgular\u0131n di\u011fer ara\u015ft\u0131rmalardaki bak\u0131\u015f a\u00e7\u0131lar\u0131n\u0131 nas\u0131l etkileyebilece\u011finden de bahsetmi\u015ftir.\u00a0\u015eimdiye kadar tek yumurta ikizlerindeki farkl\u0131l\u0131klar\u0131 ara\u015ft\u0131ran bir\u00e7ok \u00e7al\u0131\u015fma, bu bireylerin farkl\u0131 ortamda yeti\u015fmelerini ve normalde genetik olarak birbirlerinin kopyas\u0131 olduklar\u0131n\u0131 temel alarak hareket etmi\u015f, dolay\u0131s\u0131yla da ki\u015filerin fenotiplerinde veya baz\u0131 hastal\u0131klara yatk\u0131nl\u0131klar\u0131nda g\u00f6zlemlenen farkl\u0131l\u0131klar\u0131n bu ortam de\u011fi\u015fikli\u011finden kaynakland\u0131\u011f\u0131 d\u00fc\u015f\u00fcn\u00fclm\u00fc\u015ft\u00fcr.\u00a0Ancak bu konuda yap\u0131lan detayl\u0131 ara\u015ft\u0131rmalar\u0131n da yava\u015f yava\u015f ortaya \u00e7\u0131kard\u0131\u011f\u0131 gibi art\u0131k b\u00f6yle oldu\u011fu do\u011frudan varsay\u0131lamamaktad\u0131r.\u00a0<\/p>\n\n\n\n

Genetik alan\u0131 alt\u0131ndaki bir\u00e7ok konu gibi asl\u0131nda do\u011fru olmad\u0131\u011f\u0131 yava\u015f yava\u015f anla\u015f\u0131lan varsay\u0131mlar da hala ara\u015ft\u0131r\u0131lmakta ve her ge\u00e7en g\u00fcn daha fazla detay ortaya \u00e7\u0131kmaktad\u0131r. E\u011fer bu konuda daha fazla bilgi almak isterseniz kaynak\u00e7am\u0131n alt\u0131nda derledi\u011fim makale listesine de g\u00f6z atabilirsiniz. <\/p>\n\n\n\n

Kaynak\u00e7a<\/strong><\/p>\n\n\n\n

Casselman, A. (2008, Nisan 3). Identical Twins\u2019 Genes Are Not Identical<\/em>. Scientific American. https:\/\/www.scientificamerican.com\/article\/identical-twins-genes-are-not-identical\/<\/p>\n\n\n\n

Jonsson, H., Magnusdottir, E., Eggertsson, H. P., Stefansson, O. A., Arnadottir, G. A., Eiriksson, O., Zink, F., Helgason, E. A., Jonsdottir, I., Gylfason, A., Jonasdottir, A., Jonasdottir, A., Beyter, D., Steingrimsdottir, T., Norddahl, G. L., Magnusson, O. Th., Masson, G., Halldorsson, B. V., Thorsteinsdottir, U., \u2026 Stefansson, K. (2021). Differences between germline genomes of monozygotic twins. Nature Genetics<\/em>, 53<\/em>(1), 27-34. https:\/\/doi.org\/10.1038\/s41588-020-00755-1<\/p>\n\n\n\n

Kratz, C. P., Edelman, D. C., Wang, Y., Meltzer, P. S., & Greene, M. H. (2014). Genetic and epigenetic analysis of monozygotic twins discordant for testicular cancer. International Journal of Molecular Epidemiology and Genetics<\/em>, 5<\/em>(3), 135-139.<\/p>\n\n\n\n

Offord, C. (2021, Ocak 7). Identical Twins Accumulate Genetic Differences in the Womb<\/em>. The Scientist Magazine\u00ae. https:\/\/www.the-scientist.com\/news-opinion\/identical-twins-accumulate-genetic-differences-in-the-womb-68324<\/p>\n\n\n\n

Saey, T. H. (2021, Ocak 7). Some identical twins don\u2019t have identical DNA. Science News<\/em>. https:\/\/www.sciencenews.org\/article\/some-identical-twins-dont-have-identical-dna-genetics<\/p>\n\n\n\n

Ekstra Okumalar <\/strong><\/p>\n\n\n\n

  1. Van Dongen, J., Slagboom, P. E., Draisma, H. H. M., Martin, N. G. & Boomsma, D. I. The continuing value of twin studies in the omics era. Nat. Rev. Genet. <\/em>13, 640\u2013653 (2012). <\/li>
  2. Ehli, E. A. et al. De novo and inherited CNVs in MZ twin pairs selected for discordance and concordance on attention problems. Eur. J. Hum. Genet. <\/em>20, 1037\u20131043 (2012). <\/li>
  3. Baranzini, S. E. et al. Genome, epigenome and RNA sequences of monozygotic twins discordant for multiple sclerosis. Nature <\/em>464, 1351\u20131356 (2010). <\/li>
  4. Dal, G. M. et al. Early postzygotic mutations contribute to de novo variation in a healthy monozygotic twin pair. J. Med. Genet. <\/em>51, 455\u2013459 (2014). <\/li><\/ol>\n","protected":false},"excerpt":{"rendered":"

    Genetik alan\u0131nda yap\u0131lan, \u00f6zellikle de \u00e7evresel fakt\u00f6rlerin ve genetik kodun birbirlerini nas\u0131l etkiledi\u011fi ve birlikte ki\u015finin hayat\u0131n\u0131 nas\u0131l \u015fekillendirdi\u011fi \u00fczerine<\/p>\n","protected":false},"author":273,"featured_media":9790,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"acf":[],"views":643,"_links":{"self":[{"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/posts\/9787"}],"collection":[{"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/users\/273"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/comments?post=9787"}],"version-history":[{"count":2,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/posts\/9787\/revisions"}],"predecessor-version":[{"id":10519,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/posts\/9787\/revisions\/10519"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/media\/9790"}],"wp:attachment":[{"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/media?parent=9787"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/categories?post=9787"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.ulubat.org\/index.php\/wp-json\/wp\/v2\/tags?post=9787"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}