{"id":864,"date":"2020-03-24T11:02:01","date_gmt":"2020-03-24T11:02:01","guid":{"rendered":"https:\/\/uni.hi.is\/apalsson\/?p=864"},"modified":"2020-03-24T11:04:32","modified_gmt":"2020-03-24T11:04:32","slug":"icelandic-stokkbreytast-veirur-hradar-en-floknar-lifverur","status":"publish","type":"post","link":"https:\/\/uni.hi.is\/apalsson\/IS\/2020\/03\/24\/icelandic-stokkbreytast-veirur-hradar-en-floknar-lifverur\/","title":{"rendered":"Geta l\u00edfverur \u00fer\u00f3ast \u00ed st\u00f6kkum vegna st\u00f6kkbreytinga?"},"content":{"rendered":"

Upprunalega spurningin hlj\u00f3\u00f0a\u00f0i svona:<\/p>\n

Tala\u00f0 er um l\u00edfverur sem st\u00f6kkbreytast me\u00f0 t\u00ed\u00f0 og t\u00edma eftir \u00fev\u00ed hva\u00f0 st\u00f6kkbreytingin er hentug hverjum sta\u00f0 fyrir sig. Hva\u00f0 tekur eiginlega langan t\u00edma fyrir l\u00edfverur a\u00f0 st\u00f6kkbreytast e\u00f0a \u00fer\u00f3ast, eru \u00fea\u00f0 \u00e1ratugir, hundru\u00f0ir, \u00fe\u00fasundir e\u00f0a milj\u00f3n \u00e1r?<\/p><\/blockquote>\n

St\u00f6kkbreytingar<\/a> eru hr\u00e1efni \u00fer\u00f3unar l\u00edfvera, \u00fe\u00e6r eru fr\u00e1vik sem ver\u00f0a \u00ed erf\u00f0aefni<\/a> l\u00edfvera en lei\u00f0a ekki endilega til st\u00f6kka \u00ed \u00fatliti \u00feeirra e\u00f0a eiginleikum. St\u00f6kkbreytingar geta breytt \u00e1kve\u00f0num st\u00f6\u00f0um \u00ed genum<\/a> e\u00f0a jafnvel byggingu e\u00f0a samsetningu litninga. \u00deetta er hli\u00f0st\u00e6tt \u00fev\u00ed a\u00f0 sumar villur \u00ed b\u00f3kum eru einfaldar stafsetningarvillur (samanber hestur e\u00f0a gestur) \u00e1 me\u00f0an a\u00f0rar ver\u00f0a \u00feegar kj\u00f6lurinn rofnar og kaflar fara \u00e1 flakk. \u00cdslenska or\u00f0i\u00f0 st\u00f6kkbreyting er \u00e1 vissan h\u00e1tt misv\u00edsandi. Sannarlega hafa sumar st\u00f6kkbreytingar mikil \u00e1hrif \u00e1 eiginleika l\u00edfvera en flestar eru minnih\u00e1ttar. Sterkar breytingar, eins og \u00fe\u00e6r sem breyta sl\u00e9ttri baun \u00ed hrukk\u00f3tta, v\u00e6ngja\u00f0ri flugu \u00ed v\u00e6nglausa og augnlit \u00far br\u00fanum \u00ed bl\u00e1an, voru vi\u00f0fangsefni Gregors Mendel<\/a> (1822 \u20131884), Thomas H. Morgan<\/a> (1866 \u20131945) og annarra frumkv\u00f6\u00f0la erf\u00f0afr\u00e6\u00f0innar. \u00dev\u00ed var \u00ed fyrstu tali\u00f0 a\u00f0 breytingar \u00e1 erf\u00f0aefni hef\u00f0u sterk og sk\u00fdr \u00e1hrif<\/span>[1]<\/a><\/sup>. S\u00fa hugmynd var endanlega kve\u00f0in \u00ed k\u00fatinn af bandar\u00edska erf\u00f0afr\u00e6\u00f0ingnum Martin Kreitman \u00e1ri\u00f0 1983. Hann sko\u00f0a\u00f0i fyrstur manna breytileika \u00ed r\u00f6\u00f0 \u00e1kve\u00f0ins gens (Adh<\/em> \u00ed \u00e1vaxtaflugum<\/a>) og fann margfalt meiri breytileika en b\u00faast m\u00e1tti vi\u00f0 \u00fat fr\u00e1 eiginleikum \u00e1vaxtaflugnanna sem rannsaka\u00f0ar voru. Ranns\u00f3kn Kreitmans var ger\u00f0 m\u00f6guleg me\u00f0 framf\u00f6rum \u00ed sameindaerf\u00f0afr\u00e6\u00f0i sem nokkrum \u00e1ratugum s\u00ed\u00f0ar leiddu til \u00feess a\u00f0 heilu erf\u00f0amengin<\/a> voru ra\u00f0greind.<\/p>\n

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Thomas H. Morgan rannsaka\u00f0i fr\u00e1vik \u00ed formi \u00e1vaxtaflugna. Villiger\u00f0ar kvenfluga a) og b) karlfluga, og karlfluga arfhrein um galla \u00ed vestigial<\/em> geninu c).<\/p>\n<\/div>\n<\/div>\n

Erf\u00f0amengi tegunda eru misst\u00f3r, einlitna erf\u00f0amengi \u00e1vaxtaflugu er um \u00fea\u00f0 bil 180 millj\u00f3nir basa, einlitna mengi H. sapiens<\/em> er 3,2 milljar\u00f0ar basa, furur eru me\u00f0 mengi upp \u00e1 15,9 milljar\u00f0a basa<\/span>[2]<\/a><\/sup>. Ni\u00f0urst\u00f6\u00f0ur ranns\u00f3kna hafa s\u00fdnt a\u00f0 \u00ed erf\u00f0amengjum l\u00edfvera eru millj\u00f3nir e\u00f0a tugmillj\u00f3nir st\u00f6kkbreytinga en flestar \u00feeirra hafa n\u00e6stum engin \u00e1hrif \u00e1 eiginleika l\u00edfveranna<\/span>[3]<\/a><\/sup>. \u00dea\u00f0 er sta\u00f0reynd a\u00f0 enginn einstaklingur af mannkyni er laus vi\u00f0 st\u00f6kkbreytingar, ekki frekar en a\u00f0rar l\u00edfverur. En geta st\u00f6kkbreytingar l\u00e1ti\u00f0 l\u00edfverur \u00fer\u00f3ast \u00ed st\u00f6kkum? \u00der\u00f3un l\u00edfvera ver\u00f0ur vegna breytinga \u00e1 erf\u00f0asamsetningu stofna yfir margar kynsl\u00f3\u00f0ir, til d\u00e6mis \u00feegar \u00feeir lagast a\u00f0 breyttum a\u00f0st\u00e6\u00f0um. Erf\u00f0abreytileikinn er forsenda \u00fer\u00f3unar. En til a\u00f0 n\u00fdjar ger\u00f0ir veljist \u00far \u00feurfa \u00fe\u00e6r a\u00f0 vera betri en ger\u00f0irnar sem eru fyrir (n\u00e1tt\u00farulegt val). Flestar st\u00f6kkbreytingar me\u00f0 sterk \u00e1hrif \u00e1 svipfari\u00f0 eru ska\u00f0legar, \u00fe\u00e6r sker\u00f0a v\u00f6xt, \u00feroska, starfsemi lykill\u00edff\u00e6ra e\u00f0a annara kerfa. Erf\u00f0afr\u00e6\u00f0ingurinn Richard Goldschmitt (1878 \u2013 1958) haf\u00f0i samt mikla tr\u00fa \u00e1 \u00fev\u00ed a\u00f0 breytingar me\u00f0 sterk \u00e1hrif g\u00e6tu hra\u00f0a\u00f0 \u00fer\u00f3un og kalla\u00f0i sl\u00edk d\u00fdr \u201ehopeful monster\u201c, sem m\u00e6tti \u00fatleggja sem efnilegt skr\u00edmsli<\/em>, eins og vi\u00f0 t\u00f6lum um efnilegt ungmenni \u00e1 \u00edslensku. Samkv\u00e6mt hugmynd hans \u00e1ttu st\u00f6kkbreytingar sem bjuggu til sl\u00edk efnileg skr\u00edmsli, til d\u00e6mis tilbrig\u00f0i li\u00f0d\u00fdrs me\u00f0 f\u00e6tur sem breyttust \u00ed munnparta, a\u00f0 au\u00f0velda r\u00f3tt\u00e6kar breytingar \u00e1 formi l\u00edfvera. Hann taldi \u00e1kaflega \u00f3l\u00edklegt a\u00f0 finna li\u00f0d\u00fdr me\u00f0 h\u00e1lfan f\u00f3t og h\u00e1lfan munnpart \u00fev\u00ed sl\u00edk l\u00edfvera v\u00e6ri \u00f6rugglega minna h\u00e6f en villiger\u00f0in. H\u00fan v\u00e6ri verr a\u00f0l\u00f6gu\u00f0 og myndi \u00fev\u00ed n\u00e6r \u00f6rugglega deyja \u00fat. Sl\u00edkir dalir a\u00f0l\u00f6gunar eru vel \u00feekktir \u00ed \u00fer\u00f3unarfr\u00e6\u00f0i (mynd h\u00e9r fyrir ne\u00f0an). Tilg\u00e1ta hans var a\u00f0 efnileg skr\u00edmsli g\u00e6tu gert \u00fer\u00f3uninni kleift a\u00f0 komast yfir dali a\u00f0l\u00f6gunar og a\u00f0 n\u00fdja formi\u00f0 g\u00e6ti jafnvel veri\u00f0 jafn h\u00e6ft e\u00f0a h\u00e6fara en foreldra ger\u00f0in.<\/p>\n

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H\u00f3par geta veri\u00f0 vel a\u00f0laga\u00f0ir umhverfi s\u00ednu, til d\u00e6mis vegna \u00feess a\u00f0 l\u00edfverurnar eru me\u00f0 g\u00f3\u00f0a samsetningareiginleika (h\u00e6\u00f0, st\u00e6r\u00f0, hlaupageta, vei\u00f0itennur). Sl\u00edk tegund er \u00e1litin sitja \u00e1 a\u00f0l\u00f6gunartoppi (A), \u00e1 me\u00f0an tegund me\u00f0 a\u00f0ra samsetningu eiginleika er kannski \u00e1 \u00f6\u00f0rum toppi (B). H\u00f3pur me\u00f0 bl\u00f6ndu af eiginleikum tveggja tegunda lendir \u00ed dalnum milli a\u00f0l\u00f6gunartoppa og mun farnast illa \u00ed l\u00edfsbar\u00e1ttunni (l\u00edklega deyja \u00fat).<\/p>\n<\/div>\n<\/div>\n

N\u00e1tt\u00farulegt val \u00fearf margra kynsl\u00f3\u00f0ir til a\u00f0 n\u00fd ger\u00f0 ver\u00f0i allsr\u00e1\u00f0andi. Tegundir eru samsettar af st\u00f3rum stofnum og n\u00fdjar ger\u00f0ir eru alltaf sjaldg\u00e6far \u00ed upphafi sama hversu miklu h\u00e6fari sem \u00fe\u00e6r reynast en me\u00f0aleinstaklingurinn. \u00cd tilfelli efnilegra skr\u00edmsla t\u00e6ki einhverjar kynsl\u00f3\u00f0ir a\u00f0 festa n\u00fdjar ger\u00f0ir \u00ed stofninum \u00fev\u00ed li\u00f0d\u00fdr me\u00f0 n\u00fdja munnparta v\u00e6ri h\u00e6fara en ger\u00f0in \u00e1n \u00feeirra. Tilg\u00e1ta Goldschmitts er vissulega heillandi en s\u00e1 er galli \u00e1 gj\u00f6f Njar\u00f0ar a\u00f0 ranns\u00f3knir \u00e1 \u00fer\u00f3un l\u00edfvera \u00ed n\u00e1tt\u00farunni hafa ekki fundi\u00f0 d\u00e6mi um efnileg skr\u00edmsli sem hafi au\u00f0velda\u00f0 \u00fer\u00f3unina. \u00der\u00f3un \u00e1 s\u00e9r s\u00edfellt sta\u00f0, \u00ed hverri einustu kynsl\u00f3\u00f0 breytist erf\u00f0asamsetning og eiginleikar stofna. Hra\u00f0i \u00fer\u00f3unar \u00e1kve\u00f0inna einkenna veltur \u00e1 nokkrum \u00fe\u00e1ttum. Hversu algengt er afbrig\u00f0i\u00f0 \u00ed upphafi, sem n\u00e1tt\u00farulega er vali\u00f0 fyrir? Hversu sterk eru \u00e1hrif \u00e1 h\u00e6fni, \u00fea\u00f0 er a\u00f0 segja eykur sams\u00e6tan<\/a> h\u00e6fni um 1% e\u00f0a 15%? Hversu st\u00f6\u00f0ugur er val\u00fer\u00fdstingurinn?<\/span>[4]<\/a><\/sup> \u00der\u00f3un sumra eiginleika og tegunda hefur veri\u00f0 fjarska hr\u00f6\u00f0 (10-100 kynsl\u00f3\u00f0ir) \u00e1 me\u00f0an a\u00f0rar \u00fer\u00f3ast mun h\u00e6gar e\u00f0a a\u00f0 \u00fev\u00ed er vir\u00f0ist ekki breytast neitt \u00ed 100 millj\u00f3n \u00e1r, til d\u00e6mis bl\u00e1fiskur<\/a>. Andst\u00e6tt hugmynd Goldschmitts vir\u00f0ist \u00fer\u00f3un gerast \u00ed litlum skrefum, til d\u00e6mis a\u00f0 goggar \u00e1kve\u00f0innar finkutegundar minnka um 0,1 mm me\u00f0 hverri kynsl\u00f3\u00f0. \u00de\u00f3tt sannarlega s\u00e9u d\u00e6mi um a\u00f0l\u00f6gun tegunda vegna st\u00f6kkbreytinga sem hafa sterk \u00e1hrif flokkast \u00feau ekki sem efnileg skr\u00edmsli. Eitt \u00feekktasta d\u00e6mi\u00f0 um st\u00f6kkbreytingu me\u00f0 sterk \u00e1hrif er sams\u00e6ta gensins cortex<\/em> sem gerir v\u00e6ngi fetans Biston betularia<\/em> d\u00f6kka \u00ed sta\u00f0 lj\u00f3sa \u00e1 litinn. Me\u00f0 i\u00f0nv\u00e6\u00f0ingunni \u00ed Bretlandi huldust lj\u00f3sir trj\u00e1stofnar s\u00f3ti sem olli \u00fev\u00ed a\u00f0 einstaklingar me\u00f0 d\u00f6kkleitu sams\u00e6tuna ur\u00f0u h\u00e6fari en \u00feeir me\u00f0 lj\u00f3su sams\u00e6tuna. T\u00ed\u00f0ni hennar \u00f3x mj\u00f6g hratt \u00e1 nokkrum \u00e1ratugum \u00e1 \u00fears\u00ed\u00f0ustu \u00f6ld, uns d\u00f6kkleitir fetar ur\u00f0u allsr\u00e1\u00f0andi. \u00de\u00f3tt litabreytileikinn \u00ed fetanum s\u00e9 afgerandi telst hann samt ekki efnilegt skr\u00edmsli. Br\u00f3\u00f0urpartur \u00feeirra d\u00e6ma sem ranns\u00f6ku\u00f0 hafa veri\u00f0 benda til \u00feess a\u00f0 margir erf\u00f0a\u00fe\u00e6ttir, hver um sig me\u00f0 v\u00e6g \u00e1hrif \u00e1 h\u00e6fni, liggi til grundvallar a\u00f0l\u00f6gunar og \u00fer\u00f3unar l\u00edfvera. Sl\u00edkar breytingar taka fjarska langan t\u00edma, \u00fe\u00fasundir e\u00f0a hundru\u00f0ir \u00fe\u00fasunda kynsl\u00f3\u00f0a. \u00dea\u00f0 er t\u00edmi sem vi\u00f0 hinir \u00f3\u00feolinm\u00f3\u00f0u menn eigum fjarska erfitt me\u00f0 a\u00f0 skilja.<\/p>\n

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H\u00e9r m\u00e1 sj\u00e1 b\u00e6\u00f0i d\u00f6kkt og lj\u00f3st afbrig\u00f0i af fetanum Biston betularia<\/em> sem er \u00feekktasta d\u00e6mi\u00f0 um hra\u00f0ar \u00fer\u00f3unarbreytingar. Fyrir i\u00f0nv\u00e6\u00f0ingu var lj\u00f3sa afbrig\u00f0i\u00f0 alls r\u00e1\u00f0andi en s\u00f3tugir trj\u00e1stofnar sk\u00f6pu\u00f0u hagst\u00e6\u00f0ari skilyr\u00f0i fyrir d\u00f6kka afbrig\u00f0i\u00f0. Minna s\u00f3t \u00e1 seinni t\u00edmum hefur aftur gefi\u00f0 lj\u00f3sa afbrig\u00f0inu t\u00e6kif\u00e6ri.<\/p>\n<\/div>\n<\/div>\n

Samantekt<\/strong><\/p>\n