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Koja je riječ za grupu gena naslijeđenih zajedno?

Koja je riječ za grupu gena naslijeđenih zajedno?


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Znam riječi haplotip i haplogrupa, kao i genetska povezanost, ali...

Nedavno sam naišao na novu frazu koja opisuje gene koji se nasljeđuje kao grupa, i zapisao sam je, ali sada je ne mogu pronaći...

Također, postoji li riječ ili izraz za gene koji se izražavaju zajedno?


Vjerujem da mislite na operon?

U genetici, operon je funkcionalna jedinica DNK koja sadrži skup gena pod kontrolom jednog promotora. Geni se zajedno transkribiraju u lanac mRNA i ili se prevode zajedno u citoplazmi, ili se podvrgavaju spajanju kako bi se stvorile monocistronske mRNA koje se transliraju zasebno, tj. nekoliko lanaca mRNA od kojih svaki kodira jedan genski proizvod.

Postoji i pojam koji se zove supergen koji je na neki način manje striktno grupiranje, što ukazuje na blisku genetsku povezanost i mogući funkcionalni odnos.


Što je nasljednost?

Nasljednost je mjera koliko dobro razlike u genima ljudi objašnjavaju razlike u njihovim osobinama. Osobine mogu uključivati ​​karakteristike kao što su visina, boja očiju i inteligencija, kao i poremećaji poput shizofrenije i poremećaja autističnog spektra. U znanstvenom smislu, nasljednost je statistički koncept (predstavljen kao h²) koji opisuje koliko se varijacija u danoj osobini može pripisati genetskoj varijaciji. Procjena nasljednosti osobine specifična je za jednu populaciju u jednom okruženju i može se mijenjati tijekom vremena kako se okolnosti mijenjaju.

Procjene nasljednosti kreću se od nule do jedan. Nasljednost blizu nule ukazuje da je gotovo sva varijabilnost osobine među ljudima posljedica čimbenika okoliša, uz vrlo mali utjecaj genetskih razlika. Karakteristike kao što su religija, govorni jezik i političke preferencije imaju nultu nasljednost jer nisu pod genetskom kontrolom. Nasljednost bliska jedinici ukazuje da gotovo sva varijabilnost u osobini proizlazi iz genetskih razlika, uz vrlo mali doprinos okolišnih čimbenika. Mnogi poremećaji koji su uzrokovani mutacijama u pojedinačnim genima, kao što je fenilketonurija (PKU), imaju visoku nasljednost. Većina složenih osobina ljudi, kao što su inteligencija i multifaktorske bolesti, imaju nasljednost negdje u sredini, što sugerira da je njihova varijabilnost posljedica kombinacije genetskih i okolišnih čimbenika.

Nasljednost se povijesno procjenjivala iz studija blizanaca. Jednojajčani blizanci nemaju gotovo nikakve razlike u svojoj DNK, dok bratski blizanci dijele u prosjeku 50 posto svoje DNK. Ako se čini da je neka osobina sličnija kod jednojajčanih blizanaca nego kod dvojajčanih blizanaca (kada su zajedno odgajani u istom okruženju), genetski čimbenici vjerojatno igraju važnu ulogu u određivanju te osobine. Uspoređujući osobinu kod jednojajčanih blizanaca u odnosu na dvojajčane blizance, istraživači mogu izračunati procjenu njezine nasljednosti.

Nasljednost može biti teško razumjeti, stoga postoje mnoge zablude o tome što nam može, a što ne može reći o datoj osobini:

Nasljednost ne pokazuje koliki je udio osobine određen geni, a koji udio okoline. Dakle, nasljednost od 0,7 ne znači da je osobina 70% uzrokovana genetskim čimbenicima, već znači da je 70% varijabilnosti u osobini u populaciji posljedica genetskih razlika među ljudima.

Poznavanje nasljednosti neke osobine ne daje informacije o tome koji su geni ili utjecaji okoline uključeni, ili koliko su važni u određivanju osobine.

Nasljedno nije isto što i obiteljsko. Obilježje se opisuje kao obiteljsko ako je dijele članovi obitelji. Osobine se mogu pojaviti u obiteljima iz mnogo razloga osim genetike, poput sličnosti u načinu života i okolišu. Na primjer, jezik koji se govori obično se dijeli u obiteljima, ali nema genetski doprinos i stoga nije nasljedan.

Nasljednost ne daje nikakve informacije o tome koliko je lako ili teško promijeniti osobinu. Na primjer, boja kose je osobina visoke heritabilnosti, ali ju je vrlo lako promijeniti bojom.

Ako nasljeđivanje pruža tako ograničene informacije, zašto je istraživači proučavaju? Nasljednost je od posebnog interesa za razumijevanje osobina koje su vrlo složene s mnogim čimbenicima koji pridonose. Nasljednost može dati početne naznake o relativnim utjecajima "prirode" (genetika) i "njegovanja" (okoliša) na složene osobine, a istraživačima može dati mjesto da počnu razdvojiti čimbenike koji utječu na te osobine.


3. Pozadinske informacije analize

Analiza genetskih klastera predstavljena u ovom članku preuzeta je iz studije iz 2014. koju je proveo Lazaridis & Co. iz Reich Lab genetičara s Harvarda Davida Emila Reicha [vidi odjeljak ‘Izvori’]. Reich Lab je tijekom godina napravio mnogo izvrsnih radova na indoeuropskom podrijetlu. Neki od njih su malo “politički ispravljeni”, ali to je nevjerojatno nepristran rad, posebno u usporedbi s ostatkom moderne “znanosti.”

Ova konkretna analiza se kreće od K=2 do K=20 — ili, u terminima matrjoške, 2 sloja duboko do 20 slojeva duboko — pruža izvrstan pregled genetskog sastava svih ljudskih rasa, podrasa i etničke skupine. Neke su etničke skupine izostavljene, vjerojatno zbog činjenice da su u suštini genetski identične svojim susjedima (Nizozemci do Belgijanaca, na primjer).

Ova analiza je nevjerojatno koristan resurs koji pluta okolo već dugo vremena. Međutim, koliko mi je poznato, nacionalisti ga zapravo nisu toliko koristili, vjerojatno zato što je originalna grafika složena i laicima je teško interpretirati. Kako bi pomogao u tumačenju analize, moj prijatelj Sunny podijelio ju je na 19 različitih slika, jednu po “K=#” postavci, uz označavanje raznih skupina. Ako vas zbunjuju imena koja je Sunny koristila za klastere, samo provjerite u koju se rasu/podrasu/etničke skupine klasteri uklapaju. Odatle biste to trebali moći riješiti. Koliko ja znam, ionako nitko nije dao imena tim genetskim klasterima ni u kakvom službenom svojstvu. Ljudska taksonomija kao cjelina prilično je sjebana i beskorisna zbog marksoidne i globalističke subverzije.


Genetika

Geni su formirani od DNA (deoksiribonukleinske kiseline), velike molekule u obliku dvostruke spirale, čije nukleotidne baze mogu biti raspoređene na različite načine kako bi kodirale specifične informacije o karakteristikama koje gen predstavlja. Gene nose kromosomi, strukture poput niti koje se nalaze u parovima u gotovo svim živim stanicama. Geni nose specifikaciju (‘nacrt’) za potencijalni razvoj organizma. Genetski kodovi su specifični za vrstu (tako da se razmnožavanje ne može odvijati između vrsta), ali dopuštaju individualne varijacije među članovima vrste. Jedini slučajevi u kojima dva pojedinačna člana iste vrste imaju identične genetske informacije su monozigotni blizanci (pojedinci proizvedeni diobom već oplođenog jajašca) ili klonovi (aseksualna ili genetski modificirana reprodukcija).


15.1 Genetski kod

U ovom odjeljku istražit ćete sljedeća pitanja:

  • Što je "središnja dogma" sinteze proteina?
  • Što je genetski kod i kako nukleotidni slijed propisuje sekvencu aminokiselina i polipeptida?

Veza za AP ® tečajeve

Od ponovnog otkrića Mendelovog rada 1900-ih, znanstvenici su naučili mnogo o tome kako su genetski nacrti pohranjeni u DNK sposobni za replikaciju, ekspresiju i mutaciju. Baš kao što se 26 slova engleske abecede može rasporediti u nešto što se čini kao neograničen broj riječi, s novim dodanim u rječnik svake godine, četiri nukleotida DNK – A, T, C i G – mogu generirati sekvence DNK zvane geni koji određuju desetke tisuća polimera aminokiselina. Zauzvrat, ove sekvence se mogu transkribirati u mRNA i prevesti u proteine ​​koji upravljaju gotovo svakom funkcijom stanice. Genetski kod se odnosi na DNK abecedu (A, T, C, G), RNA abecedu (A, U, C, G) i polipeptidnu abecedu (20 aminokiselina). Ali kako geni smješteni na kromosomu u konačnici proizvode polipeptid koji može rezultirati fizičkim fenotipom kao što je boja kose ili očiju – ili bolest poput cistične fibroze ili hemofilije?

Središnja dogma opisuje normalan tijek genetskih informacija od DNK do mRNA do proteina: DNK u genima specificira sekvence mRNA koje, zauzvrat, određuju sekvence aminokiselina u proteinima. Proces zahtijeva dva koraka, transkripciju i prijevod. Tijekom transkripcije, geni se koriste za stvaranje glasničke RNA (mRNA). Zauzvrat, mRNA se koristi za usmjeravanje sinteze proteina tijekom procesa translacije. Translacija također zahtijeva dvije druge vrste RNA: prijenosnu RNA (tRNA) i ribosomalnu RNA (rRNA). Genetski kod je trostruki kod, pri čemu se svaki RNA kodon sastoji od tri uzastopna nukleotida koji određuju jednu aminokiselinu ili oslobađanje novoformiranog polipeptidnog lanca, na primjer, mRNA kodon CAU specificira aminokiselinu histidin. Kod je degeneriran, odnosno neke aminokiseline su specificirane s više od jednog kodona, poput sinonima koje proučavate u razredu engleskog (različite riječi, isto značenje). Na primjer, CCU, CCC, CCA i CCG su svi kodoni za prolin. Važno je zapamtiti da je isti genetski kod univerzalan za gotovo sve organizme na Zemlji. Male varijacije u dodjeli kodona postoje u mitohondrijima i nekim mikroorganizmima.

Odstupanja od jednostavne sheme središnje dogme otkrivaju se dok istraživači istražuju ekspresiju gena novom tehnologijom. Na primjer, virus ljudske imunodeficijencije (HIV) je retrovirus koji svoje genetske informacije pohranjuje u jednolančane RNA molekule. Nakon infekcije stanice domaćina, virusno kodirani enzim, reverzna transkriptaza, koristi RNA kao šablonu za sintezu DNA. Virusna DNK se kasnije transkribira u mRNA i prevodi u proteine. Neki RNA virusi kao što je virus gripe nikada ne prolaze DNK korak. RNA genom je repliciran RNA-ovisnom RNA polimerazom koja je virusno kodirana.

Sadržaj predstavljen u ovom odjeljku podržava ciljeve učenja iznesene u Velikoj ideji 1 i Velikoj ideji 3 okvira AP ® biološkog kurikuluma. Ciljevi učenja spajaju sadržaj osnovnog znanja s jednom ili više od sedam znanstvenih praksi. Ovi ciljevi učenja pružaju transparentnu osnovu za tečaj AP ® biologije, zajedno s laboratorijskim iskustvima temeljenim na upitima, nastavnim aktivnostima i ispitnim pitanjima AP ®.

Velika ideja 1 Proces evolucije pokreće raznolikost i jedinstvo života.
Trajno razumijevanje 1.B Organizmi su povezani linijama podrijetla od zajedničkog podrijetla.
Osnovno znanje 1.B.1 Organizmi dijele mnoge očuvane temeljne procese i značajke koje su se razvile i danas su široko rasprostranjene među organizmima.
Znanstvena praksa 3.1 Student može postavljati znanstvena pitanja.
Znanstvena praksa 7.2 Učenik može povezati koncepte u i preko domene(a) kako bi generalizirao ili ekstrapolirao u i/ili preko trajnih razumijevanja i/ili velikih ideja.
Cilj učenja 1.15 Student je sposoban opisati specifične primjere očuvanih jezgri bioloških procesa i značajki koje dijele sve domene ili unutar jedne domene života, te kako ti zajednički, očuvani temeljni procesi i značajke podržavaju koncept zajedničkog porijekla za sve organizme.
Velika ideja 3 Živi sustavi pohranjuju, dohvaćaju, prenose i odgovaraju na informacije bitne za životne procese.
Trajno razumijevanje 3.A Nasljedne informacije osiguravaju kontinuitet života.
Osnovno znanje 3.A.1 DNK, au nekim slučajevima i RNA, primarni je izvor nasljednih informacija.
Znanstvena praksa 6.5 Student može ocijeniti alternativna znanstvena objašnjenja.
Cilj učenja 3.1 Student je sposoban konstruirati znanstvena objašnjenja koja koriste strukturu i funkcije DNK i RNA kako bi poduprla tvrdnju da su DNK i, u nekim slučajevima, da su RNA primarni izvori nasljednih informacija.

Podrška učiteljima

Središnja dogma potvrđena je mnogim eksperimentima. Protok informacija od DNK do mRNA do polipeptida uobičajena je shema u svim stanicama, i prokariotskim i eukariotskim. Informacije u DNK sadržane su u slijedu dušičnih baza. Sljedeće pitanje je, kako se slijed dušičnih baza prevodi u aminokiseline? Kombinacija dva od četiri slova daje 16 mogućih aminokiselina (4 2 = 16), na primjer, AA ili AC, ali postoji 20 aminokiselina. Kombinacija triju baza daje 64 moguća skupa (4 3 = 64), na primjer, AAA ili AAC. Kombinacija tri baze u nizu je kodon ili "trojke". To dovodi do više nego dovoljno kombinacija za 20 uobičajenih kiselina. Neke aminokiseline su određene jednim kodonom, na primjer, metionin i triptofan, druge su kodirane s do šest neovisnih kodona, na primjer, leucin.

Iako sinteza proteina slijedi istu opću shemu u prokariota i eukariota, detaljni mehanizam svakog od njih može biti prilično različit. Prisutnost nuklearne membrane dodaje sloj složenosti procesu. Kod prokariota, transkripcija i prijevod su usko povezani. Čim se 5'-kraj mRNA transkribira s predloška lanca DNA, ribosomi se mogu zakačiti za njega i počinje sinteza polipeptida. Eukariotske stanice koriste složeniji niz koraka. Enzim RNA polimeraza tvori kompleks inicijacije transkripcije s mnogim proteinima koji se nazivaju transkripcijski čimbenici. Produkt transkripcije, mRNA prolazi kroz nekoliko modifikacija koje mijenjaju njegovu stabilnost i olakšavaju izvoz iz jezgre. Ovi dodatni koraci omogućuju veću kontrolu nad ekspresijom gena. Iako prokariotska mRNA općenito nije modificirana, lanci eukariotske mRNA podliježu dodavanju metil-guanozinske kapice na 5'-kraju i poli-adenozinskog repa na 3'-kraju, bez čega ne mogu izaći iz jezgre. mRNA također prolazi kroz spajanje kako bi se uklonili introni, regije gena koje nisu kodirane za proteine. Translacija proteina ovisi o prisutnosti ribosoma, mRNA, punog kompleta tRNA molekula, mnogih enzima i mnogih proteinskih čimbenika. Kako se polipeptid sintetizira, počinje se savijati u svoju trodimenzionalnu strukturu. Daljnje modifikacije osigurat će da protein bude potpuno funkcionalan i dopremljen na odredište.

Pitajte učenike što je dogma. Služit će kao uvod u odstupanja od Središnje dogme. Virusi pokazuju brojne varijacije. Virus ljudske imunodeficijencije (HIV) je retrovirus. Njegov genom je kodiran u RNA molekulama koje služe kao predložak za sintezu DNK virusno kodiranim enzimom zvanim reverzna transkriptaza. Istaknite da je ovaj enzim, koji se ne nalazi u ljudima, meta mnogih lijekova protiv HIV-a. Virus gripe nosi nekodirajuće niti RNA molekula koje se u stanici domaćinu repliciraju RNA-ovisnom RNA polimerazom, enzimom koji je kodiran u virusnom genomu. U slučaju virusa gripe uopće nema DNK stadija. Tijek informacija je od RNA do RNA do proteina. Bliže “domu”, telomere, krajevi linearnih kromosoma u eukariota, repliciraju se posebnim enzimom, telomerazom, koja sintetizira DNK iz RNA šablona.

Baš kao što prenosimo informacije pomoću slova i brojeva, stanica prenosi informacije pomoću molekula. Naglasite sličnosti između pisanja i genetskog koda. Recite učenicima da je veći dio vokabulara molekularne genetike posuđen iz uređivanja: transkripcija, prijevod, lektura, missense, besmislica itd.

Iako se u poglavlju ne koristi izraz "otvoreni okvir za čitanje", povežite ga sa slikom 15.4. Otvoreni okvir čitanja je DNK sekvenca koja slijedi početni kodon i završava stop kodonom. Dugi otvoreni okvir za čitanje vjerojatno je gen.

Podrška učiteljima

Učenici brkaju rječnik koji se koristi za opisivanje Središnje dogme. Kopiranje informacija iz DNK u RNA je transkripcija jer je jezik isti. Oba su konstruirana pomoću nukleotida. Kada se sintetizira polipeptid, gradivni blokovi ili "slova" prelaze na aminokiseline. To je prijevod. Iako nije sasvim identičan, pokažite učenicima primjer sličan sljedećem:

Pas da Pas (transkripcija) u Canis (prijevod)

Prve dvije riječi predstavljaju transkripciju. Slova su samo kopirana. Posljednja riječ ima isto značenje, "pas" na latinskom, ali sada je jezik drugačiji.

Razmislite o korištenju riječi "suvišan" kako biste objasnili značenje riječi "degeneriran" u ovom kontekstu. Učenici brkaju činjenicu da je kod degeneriran – nekoliko kodona može kodirati istu aminokiselinu – s činjenicom da je genetski kod univerzalan, što znači da se isti kodon, AUG kao primjer, prevodi kao metionin u svim stanicama. Zabuna nastaje jer učenici istovremeno uče dva pojma. Navedite primjere promjena kodona koje rezultiraju istim aminokiselinama. Iako je slijed gena različit, polipeptid je isti. Podsjetite učenike da svaki kodon specificira jednu aminokiselinu, ali obrnuto nije točno. Ovisno o aminokiselini, više od jednog kodona će se prevesti u istu aminokiselinu.

Objasnite da se mnogi proteini od interesa sintetiziraju u bakterijama i kvascima umetanjem gena za proteine ​​u ekspresijski sustav domaćina. To je moguće jer je kod univerzalan. Ako je gen koji kodira ljudski inzulin umetnut u kromosome E coli, bakterije će sintetizirati ljudski inzulin.

Podrška učiteljima

Dajte učenicima primjere kodona i zamolite ih da pronađu odgovarajuću aminokiselinu. Upozorite im da su tipografske pogreške veliki izvor mutacija. Trebali bi pažljivo lektorirati svoje sekvence.

Pitanja za izazov znanstvene prakse sadrže dodatna testna pitanja za ovaj odjeljak koja će vam pomoći da se pripremite za AP ispit. Ova pitanja odnose se na sljedeće standarde:
[APLO 3.4][APLO 3.25]

Stanični proces transkripcije stvara glasničku RNA (mRNA), mobilnu molekularnu kopiju jednog ili više gena s abecedom A, C, G i uracil (U). Prijevod predloška mRNA pretvara genetske informacije temeljene na nukleotidima u proteinski proizvod. Proteinske sekvence sastoje se od 20 uobičajenih aminokiselina, stoga se može reći da se proteinska abeceda sastoji od 20 slova (slika 15.2). Svaka aminokiselina je definirana slijedom od tri nukleotida koji se naziva triplet kodon. Različite aminokiseline imaju različite kemije (kao što su kisele naspram bazične, ili polarne i nepolarne) i različita strukturna ograničenja. Varijacije u slijedu aminokiselina uzrokuju ogromne varijacije u strukturi i funkciji proteina.

Središnja dogma: DNK kodira RNA RNA kodira protein

Tijek genetskih informacija u stanicama od DNK do mRNA do proteina opisan je Središnjom dogmom (slika 15.3), koja kaže da geni određuju slijed mRNA, koji zauzvrat određuju slijed proteina. Dekodiranje jedne molekule u drugu obavljaju specifični proteini i RNA. Budući da su informacije pohranjene u DNK tako središnje za staničnu funkciju, intuitivno je logično da će stanica napraviti kopije mRNA tih informacija za sintezu proteina, dok samu DNK zadrži netaknutom i zaštićenom. Kopiranje DNA u RNA je relativno jednostavno, s tim da se jedan nukleotid dodaje u lanac mRNA za svaki nukleotid očitan u lancu DNA. Prijevod u protein je malo složeniji jer tri mRNA nukleotida odgovaraju jednoj aminokiselini u polipeptidnoj sekvenci. Međutim, prijevod u protein je još uvijek sustavan i kolinearan, tako da nukleotidi 1 do 3 odgovaraju aminokiselini 1, nukleotidi 4 do 6 odgovaraju aminokiselini 2 i tako dalje.

Genetski kod je degeneriran i univerzalan

S obzirom na različit broj "slova" u mRNA i proteinskim "abecedama", znanstvenici su teoretizirali da kombinacije nukleotida odgovaraju pojedinačnim aminokiselinama. Dupleti nukleotida ne bi bili dovoljni za specificiranje svake aminokiseline jer postoji samo 16 mogućih dvonukleotidnih kombinacija (4 2 ). Nasuprot tome, postoje 64 moguća nukleotidna tripleta (4 3 ), što je daleko više od broja aminokiselina. Znanstvenici su teoretizirali da su aminokiseline kodirane nukleotidnim trojkama i da je genetski kod degeneriran. Drugim riječima, određena aminokiselina može biti kodirana s više od jednog nukleotidnog tripleta. To je kasnije eksperimentalno potvrđeno Francis Crick i Sydney Brenner su koristili kemijski mutagen proflavin da umetnu jedan, dva ili tri nukleotida u gen virusa. Kada su umetnuta jedan ili dva nukleotida, sinteza proteina je potpuno ukinuta. Kada su umetnuta tri nukleotida, protein je sintetiziran i funkcionalan. To je pokazalo da tri nukleotida određuju svaku aminokiselinu. Ovi nukleotidni trojci nazivaju se kodoni. Umetanje jednog ili dva nukleotida potpuno je promijenilo okvir čitanja tripleta, mijenjajući tako poruku za svaku slijedeću aminokiselinu (slika 15.4). Iako je umetanje tri nukleotida uzrokovalo umetanje dodatne aminokiseline tijekom translacije, očuvan je integritet ostatka proteina.

Znanstvenici su mukotrpno riješili genetski kod prevođenjem sintetskih mRNA in vitro i sekvenciranjem proteina koje su naveli (slika 15.5).

Uz upute za dodavanje specifične aminokiseline u polipeptidni lanac, tri od 64 kodona prekidaju sintezu proteina i oslobađaju polipeptid iz translacijskih strojeva. Ti se trojci nazivaju besmislenim kodonima ili stop kodonima. Drugi kodon, AUG, također ima posebnu funkciju. Osim što specificira aminokiselinu metionin, ona također služi kao početni kodon za pokretanje translacije. Okvir čitanja za translaciju postavlja AUG početni kodon blizu 5' kraja mRNA.

Genetski kod je univerzalan. Uz nekoliko iznimaka, gotovo sve vrste koriste isti genetski kod za sintezu proteina. Očuvanje kodona znači da bi se pročišćena mRNA koja kodira globinski protein kod konja mogla prenijeti u stanicu tulipana, a tulipan bi sintetizirao konjski globin. To što postoji samo jedan genetski kod snažan je dokaz da sav život na Zemlji dijeli zajedničko podrijetlo, posebno ako se uzme u obzir da postoje oko 10 84 moguće kombinacije od 20 aminokiselina i 64 triplet kodona.

Poveznica na učenje

Transkribirajte gen i prevedite ga u protein koristeći komplementarno uparivanje i genetski kod na ovom mjestu.

  1. Ako postoji pogreška u prijevodu, ispravni lipidi neće biti napravljeni za signalizaciju, skladištenje energije ili za obavljanje vitalnih funkcija. To može uzrokovati nasljedne bolesti i bolesti povezane s dobi.
  2. Translacija je proces u kojem se određeni segment DNA kopira u RNA (mRNA) pomoću enzima RNA polimeraze. Pogreška u takvom kopiranju može dovesti do raznih nasljednih i dobnih bolesti.
  3. Translacija je proces koji ribosomi koriste za sintezu proteina iz aminokiselina. Ako postoji pogreška u ovom procesu, ispravni proteini neće biti napravljeni za izgradnju važnog tjelesnog tkiva ili obavljanje vitalnih funkcija, što dovodi do nasljednih bolesti i bolesti povezanih s dobi.
  4. Translacija je proces koji Golgijeva tijela koriste za sintezu proteina iz aminokiselina. Ako postoji greška u ovom procesu, ispravni proteini neće biti napravljeni za izgradnju važnog tjelesnog tkiva ili obavljanje vitalnih funkcija.

Povezivanje znanstvene prakse za AP® tečajeve

Razmisli o tome

  • Lanac DNA ima nukleotidnu sekvencu 3'……GCT GTC AAA TTC GAT……5'. Koji je slijed mRNA koji je komplementaran ovom slijedu DNK? Koristeći tablicu kodona u tekstu, odredite slijed aminokiselina koje se mogu generirati iz ovog lanca DNK.
  • Kako degeneracija genetskog koda čini stanice manje ranjivim na mutacije? Koja je prednost degeneracije u odnosu na negativan utjecaj slučajnih mutacija na prirodnu selekciju i evoluciju?

Podrška učiteljima

Prvo pitanje je primjena Cilja učenja 3.1 i Znanstvene prakse 6.5 jer učenici objašnjavaju kako se jezik DNK može transkribirati i prevesti u slijed aminokiselina.

Drugi skup pitanja je primjena Cilja učenja 1.15 i Znanstvene prakse 3.1 jer se od učenika traži da postave pitanja o univerzalnom genetskom kodu i utjecaju njegove degeneracije na mutacije.

Odgovor

  • 3'...GCT GTC AAA TTC GAT...5'
  • mRNA 5'……CGA CAG UUU AAG CUA……3'
  • peptid…Arg Gln Phe Lys Leu……

Vjeruje se da je degeneracija stanični mehanizam za smanjenje negativnog utjecaja slučajnih mutacija. Kodoni koji određuju istu aminokiselinu obično se razlikuju samo po jednom nukleotidu. Osim toga, aminokiseline s kemijski sličnim bočnim lancima kodirane su sličnim kodonima. Ova nijansa genetskog koda osigurava da jednonukleotidna supstitucijska mutacija može ili specificirati istu aminokiselinu, ali nema učinka ili specificirati sličnu aminokiselinu, sprječavajući da protein postane potpuno nefunkcionalan.

Povezivanje znanstvene metode

Što ima više DNK: kivi ili jagoda?

Pitanje: Bi li kivi i jagoda približno iste veličine (slika 15.6) također imali približno istu količinu DNK?

Pozadina: Geni se prenose na kromosomima i sastoje se od DNK. Svi sisavci su diploidni, što znači da imaju dvije kopije svakog kromosoma. Međutim, nisu sve biljke diploidne. Obična jagoda je oktoploidna (8n) a kultivirani kivi je heksaploid (6n). Istražite ukupan broj kromosoma u stanicama svakog od ovih plodova i razmislite kako bi to moglo odgovarati količini DNK u jezgri stanica ovih plodova. Pročitajte o tehnici izolacije DNK da biste razumjeli kako svaki korak u protokolu izolacije pomaže oslobađanju i taloženju DNK.

Hipoteza: Pretpostavite da li biste mogli otkriti razliku u količini DNK od jagoda i kivija slične veličine. Što mislite koje voće bi dalo više DNK?

Testirajte svoju hipotezu: Izolirajte DNK iz jagode i kivija slične veličine. Provedite pokus u najmanje tri primjerka za svako voće.

  1. Pripremite bočicu pufera za ekstrakciju DNK od 900 mL vode, 50 mL deterdženta za suđe i dvije žličice kuhinjske soli. Miješajte preokretom (začepite i okrenite nekoliko puta naopako).
  2. Jagodu i kivi sameljite ručno u plastičnoj vrećici ili žbukom ili metalnom posudom i krajem tupim instrumentom. Samljeti najmanje dvije minute po voću.
  3. Dodajte 10 mL pufera za ekstrakciju DNK svakom voću i dobro miješajte najmanje jednu minutu.
  4. Uklonite stanične ostatke filtriranjem svake mješavine voća kroz gazu ili poroznu tkaninu i u lijevak postavljen u epruvetu ili odgovarajuću posudu.
  5. U epruvetu ulijte ledeno hladan etanol ili izopropanol (alkohol za trljanje). Trebali biste promatrati bijelu, precipitiranu DNK.
  6. Sakupite DNK iz svakog voća tako što ćete ga namotati oko zasebnih staklenih šipki.

Zabilježite svoja zapažanja: Budući da ne mjerite kvantitativno volumen DNK, možete za svaki pokus zabilježiti jesu li dva ploda proizvela istu ili različitu količinu DNK što je vidljivo na oko. Ako je jedno ili drugo voće proizvelo osjetno više DNK, zabilježite i to. Odredite jesu li vaša zapažanja u skladu s nekoliko komada svakog voća.

Analizirajte svoje podatke: Jeste li primijetili očitu razliku u količini DNK koju proizvodi svako voće? Jesu li vaši rezultati bili ponovljivi?

Izvući zaključak: S obzirom na ono što znate o broju kromosoma u svakom voću, možete li zaključiti da broj kromosoma nužno korelira s količinom DNK? Možete li identificirati neke nedostatke ovog postupka? Da ste imali pristup laboratoriju, kako biste mogli standardizirati svoju usporedbu i učiniti je kvantitativnijom?

Zamislite da postoji 200 uobičajenih aminokiselina umjesto 20. S obzirom na ono što znate o genetskom kodu, koja bi bila najkraća moguća duljina kodona? Objasniti.

Razgovarajte o tome kako degeneracija genetskog koda čini stanice otpornijima na mutacije.


Bitna literatura za depresiju

Zašto naši najbliži obiteljski odnosi mogu dovesti do depresije

Nove studije povezuju prekomjernu upotrebu Facebooka s depresijom

Daljnje skupine gena povezane su sa sinaptičkim funkcijama (sinapsa je mjesto gdje se neuroni međusobno povezuju), oblicima u koje neuroni mogu izrasti ("neuronska morfogeneza") i nizom gena uključenih u druge aspekte razvoja stanice, staničnu komunikaciju, upala i imunološki odgovor, a posebno geni koji upravljaju spavanjem i budnošću, za koje se smatra da su kritični u većini oblika depresije. Kako se svi ovi geni čitaju u stvarne funkcionalne proteine ​​u cijelom mozgu, znajući gdje se nalaze i što rade predstavlja mogućnosti za kliničku intervenciju. U isto vrijeme, niti jedan od ovih gena nije baš specifičan za depresiju. Kako depresija ima mnogo oblika i veličina i preklapa se s mnogim drugim medicinskim i psihijatrijskim stanjima, nije iznenađujuće da se geni depresije također preklapaju s onima drugih stanja, ne samo shizofrenije, već i anksioznih poremećaja i još mnogo toga.

Intervencije mogu biti u obliku lijekova koji na neki način stupaju u interakciju s tim proteinima ili koji kompenziraju abnormalnu aktivnost, ili genetske terapije za promjenu ili zamjenu neispravnih gena. Razumijevanje kako su specifične funkcije, kao što je upala, disregulirane na genetskoj razini, omogućuje bolje razumijevanje načina na koji se događaju različite vrste depresije i što se može učiniti kako bi se problemi povezani s tom funkcijom ublažili na vrlo ciljani način. Za ilustraciju, ne bi svi tretmani koji smanjuju upalu poboljšali depresiju, ali razumijevanje koji geni povećavaju rizik od depresije može identificirati načine za modificiranje specifičnih puteva upale koji će smanjiti simptome depresije.

Razvoj genomike

Kao i kod drugih zdravstvenih stanja, razumijevanje genetike depresije otvara vrata za dijagnozu, prevenciju i liječenje. Kako se genetska baza podataka širi, istraživačke tehnike slične onima u trenutnoj studiji mogu se koristiti za pregled drugih stanja, uključujući anksiozni poremećaj i ADHD. Farmakogenomika, na primjer, koja je sada u redovnoj kliničkoj upotrebi, omogućuje nam donošenje bolje informiranih odabira lijekova na temelju individualne genetske analize, štedeći vrijeme i smanjujući rizik od nuspojava (“nuspojava”) u usporedbi s odabirom lijekova koji se temelji isključivo na kliničkom iskustvu i pokušaj i pogreška.

As disease models continue to be developed and refined, clinical tools based on genetic and environmental analysis will allow for more accurate diagnosis of depression and better treatment, the ultimate in personalized medicine. Testing for the various genes identified above and others will become routine — for multiple diseases, as well as for performance enhancement purposes. It will be possible via genetic and other information to identify early on who is at risk for developing depression and take preventive steps, providing environmental and potentially medical interventions, or even individualized genetic therapies, to keep depression from happening in the first place. Ethical questions notwithstanding, as with other inherited traits, it may be possible to select embryos with lower genetic risk for mental illness, or even modify genes around the time of conception to achieve desired outcomes.

Facebook image: Vibe Images/Shutterstock

LinkedIn image: Ruslan Guzov/Shutterstock

The Major Depressive Disorder Working Group of the Psychiatric Genomics Consortium. Genome-wide association analyses identify 44 risk variants and refine the genetic architecture of major depression. Nature Genetics, published online April 26, 2018. doi:10.1038/s41588-018-0090-3


What Twins Can Teach Us About Genetic and Environment Influences

  • Identical and fraternal twins can provide insight into the effects of nature and nurture on factors such as eye color, intelligence, and autism.
  • The environment can sometimes "override" genetic advantages. For example, IQ is highly heritable, but growing up in an impoverished household can lead to large discrepancies in twins' IQ.
  • Conjoined twins have different personalities and preferences despite sharing the immediate environment and even their body parts.

My friends Karen and Kelly are identical twins. Needless to say, they look a lot alike, both with dirty blond hair and friendly blue eyes. But they also act alike they are voracious readers of mostly non-fiction, they laugh at the same jokes, they are both vegetarians, they both have doctoral degrees, they are both runners, hikers, and they are both prone to anxiety.

However, despite these striking similarities, they are also different people: Karen is a college professor, and Kelly is a physical therapist Kelly likes camping while Karen doesn’t like to sleep in tents Karen is enjoys drinking wine, while Kelly doesn’t care much for alcohol.

Seeing Karen and Kelly together is an extraordinary experience. If you’ve ever met or even seen a pair of twins, you would probably agree that they are undeniably special. Indeed, twins have dazzled us since the beginning of time. They held a special status in ancient Greek and Roman mythology, often representing the forces of good and evil. The fabled twins Romulus and Remus were even credited with founding the Roman Empire. But it wasn’t until the late 1800’s that Sir Francis Galton recognized the significance of twins, not for the study of good versus evil, but for the classic question of nature versus nurture. Over the course of the next 150 years, twins have made amazing contributions to what we know about the body and the brain, giving us important insights into who we are and how we get there.

As I’m sure you already know, there are two types of twins: identical and fraternal. Identical twins are born when a single fertilized egg splits in two. That means when a single sperm and a single egg come together—as they would for any other baby—it splits in half, producing two identical babies instead of one. We call them identical twins because they literally share all of the same genes. Scientists also call them monozygotic twins, because they come from a single zygote or embryo. As Karen likes to point out, she and Kelly were once a “single cell.”

Fraternal twins come from two different sperm and two different eggs. Usually, women only release a single egg during each monthly cycle, which is why most mothers get pregnant with one baby at a time. In rare cases, she might release two eggs instead of one, and if they both get fertilized, what results is fraternal, or dizygotic (from two zygotes) twins. Fraternal twins are like siblings in every way except that they share a womb. They have some of the same genes, but only about 50% since they come from two different sperm and two different eggs.

Heritability in Fraternal and Identical Twins

Because both fraternal and identical twins theoretically share the same environment—the same family, the same home, and the same community—looking at the differences between identical and fraternal twins can tell us something about the effects of nature versus nurture on a number of factors. Let’s say you want to know whether eye color is heritable. You would likely find out that in identical twins, there is a 100% chance that they will share the same eye color, but for fraternal twins, it is closer to 70%. Since the percentage is higher in identical than in fraternal twins, this tells you that genetics plays a role (and in this case, a major one) in determining eye color.

In the case of IQ, the relationship between IQ in identical twins can be over 80%, where it is closer to 50% in fraternal twins. This tells us that, like eye color, heritability plays an important role in IQ, there’s more room for the environment to play a role as well, since the relationship isn’t 100% in twins who share all of the same genes.

Using this strategy, studies on twins have given us a lot of important information about human behavior, the brain, and the body. For example, twin studies have shown us the approximate heritability of type 1 and type 2 diabetes, schizophrenia, and different types of cancer (e.g., Castillo-Fernandez, Spector, & Bell, 2014). In fact, a group of researchers from Great Britain recently studied twins to find out what the likelihood is that if one twin was diagnosed with autism that the second one would be too. They found that genetic factors accounted for the majority of the incidence of autism in their twin-based population.

Despite what we know about the heritability of various illnesses based on twin studies, twin studies have also told us a lot about the impact that the environment can make on who we are. This research has shown that sometimes the heritability of a certain trait or behavior can vary based on variations in the environment in which we grow up.

For example, as mentioned above, several twin studies have reported that IQ can be highly heritable, but it turns out that this is only true in certain environments—namely the environments of children who are raised in middle class, or wealthy households. For impoverished families who live in more high-risk neighborhoods, the heritability of IQ is nearly zero (Turkheimer et al., 2003). In other words, if given every opportunity for your genetic endowment to flourish, IQ is mostly based on your genetics. But, if the environment is riskier, any advantages your biology might bestow on you get overwhelmed by the circumstances in which you’re surrounded.

Further, while we assume that both identical and fraternal twins share the same environment, there are always aspects of the environment that are unshared, and these unshared experiences can have a major impact on our behavior. Indeed, even identical twins are never treated in exactly the same way, and don’t have exactly the same experiences. One of them might go to a basketball game with a friend while the other stays home, which piques a new interest in playing basketball for one twin and not the other. One twin might get more positive feedback in school for their math ability, which leads one twin to excel more in math than the other. These are just a few examples, but all of these tiny unshared experiences add up over the course of the lifetime, shaping different individuals with different wants, needs, likes, and dislikes.

Conjoined Twins

There is no better example of the impact of the unshared environment than of conjoined twins. Conjoined twins start out just like identical twins, where a single fertilized egg splits in two. However, for conjoined twins, the egg doesn’t fully separate into two individuals, and instead, remains physically connected, most often at the chest, abdomen or pelvis. Like monozygotic twins, conjoined twins share the same genes, but they also share parts of their bodies, or in essence, their physical and social environments.

Perhaps the most well-known pair of conjoined twins in the mainstream media are Abby and Brittney Hensel. Abby and Brittney were born in 1990, and each has a separate head, heart, lungs, spine, stomach, and spinal cord, but they share two arms, legs, large intestine, bladder and reproductive organs. Given that they share a body, and most importantly, a single pair of arms and legs, they have to coordinate everything they do. In fact, each twin manages only one side of their body, making all movements an amazing act of teamwork, yet they can walk, run, swim, play basketball, and even drive a car.

What is most interesting about the Hensel twins is that even with a shared “environment”—or in this case, a shared body—Brittney and Abby are different. They have a seamstress to make clothes for their unique body, each outfit containing separate necklines to emphasize their individuality. One twin would prefer to live in a city, while the other would opt for the calmness of a suburb. Although they both majored in education in college, they each had a different focus. And while they sometimes share meals out of pure convenience, they like different foods, and often prepare themselves different meals.

Altogether, this suggests that while twins may share the same genes, there are parts of their lives that are also unshared, leading to two distinct individuals. Thus, studying twins can tell us about how to predict and potentially treat various genetic illnesses and how our genes might mold our behavior, while at the same time, also shed light on how the environment might work hand in hand with genetic makeup to make us individuals.

So the next time you see your twin friends or twin family members, or pass by a set of identical twins on the street, you can not only marvel at their amazing likeness, but also at the extraordinary circumstances that have made them each unique.

Castillo-Fernandez, J. E., Spector, T. D., & Bell, J. T. (2014). Epigenetics of discordant monozygotic twins: implications for disease. Genome medicine, 6(7), 1-16.

Turkheimer, E., Haley, A., Waldron, M., d'Onofrio, B., & Gottesman, I. I. (2003). Socioeconomic status modifies heritability of IQ in young children. Psychological science, 14(6), 623-628.


Genetic Engineering

Genetic engineering involves isolating individual DNA fragments, coupling them with other genetic material, and causing the genes to replicate themselves. Introducing this created complex to a host cell causes it to multiply and produce clones that can later be harvested and used for a variety of purposes. Current applications of the technology include medical investigations of gene structure for the control of genetic disease, particularly through antenatal diagnosis. The synthesis of hormones and other proteins (e.g., growth hormone and insulin), which are otherwise obtainable only in their natural state, is also of interest to scientists. Applications for genetic engineering include disease control, hormone and protein synthesis, and animal research.

International Codes and Ethical Issues for Society

An international code of ethics for genetic research was first established in the World Medical Association's Declaration of Helsinki in 1964. The guide prohibited outright most forms of genetic engineering and was accepted by numerous U.S. professional medical societies, including the American Medical Association (AMA).In 1969 the AMA promulgated its own ethical guidelines for clinical investigation, key provisions of which conflicted with the Helsinki Declaration. For example, the AMA guidelines proposed that when mentally competent adults were found to be unsuitable subjects for genetic engineering studies, minors or mentally incompetent subjects could be used instead. The Helsinki Declaration did not condone testing on humans.

The growth of genetic engineering in the 1970s aroused international concern, but only limited measures were taken by governments and medical societies to control it. Concern focused on the production of dangerous bacterial mutants that could be used as harmful eugenics tools or weapons. The Genetic Manipulation Advisory Group was established in England based on the recommendations of a prominent medical group, the Williams Committee. Scientists were required to consult this group before carrying out any activity involving genetic manipulation in England. Additional measures required scientific laboratories throughout the world to include physical containment labs to prevent manipulated genes from escaping and surviving in natural conditions. These policies were subsequently adopted in the United States.

The Breakdown of Regulation: Genetic Inventions and Patents in the United States

In 1980 the Supreme Court created an economic incentive for companies to develop genetically engineered products by holding that such products could be patented. U Diamond v. Chakrabarty, 447 U.S. 303, 100 S. Ct. 2204, 65 L. Ed. 2d 144, the Court held that a patent could be issued for a novel strain of bacteria that could be used in the cleanup of oil spills. In 1986, the u.s. department of agriculture approved the sale of the first living genetically altered organism. The virus was used as a pseudorabies vaccine, from which a single gene had been cut. Within the next year, the U.S. Patent and Trademark Office announced that nonnaturally occurring, nonhuman, multicellular living organisms, including animals, were patentable under the Patent Act of 1952 (35 U.S.C.A. § 101).

The Department of Agriculture formally became involved in genetic engineering in April of 1988, when the Patent and Trademark Office issued the first animal patent, granted on a genetically engineered mouse used in cancer research. U.S. scientists began experiments with the genetic engineering of farm animals, such as creating cows that would give more milk, chickens that would lay more eggs, and pigs that would produce leaner meat. These developments only raised more objections from critics who believed that genetic experimentation on animals violated religious, moral, and ethical principles. In spite of the controversy, the U.S. House of Representatives approved the Transgenic Animal Patent Reform bill on September 13, 1988. The bill would have allowed exempted farmers to reproduce, use, or sell patented animals, although it prohibited them from selling germ cells, semen, or embryos derived from animals. However, the Senate did not vote on the act and so it did not become law.

Significant State Laws

Certain states have passed laws restricting genetic engineering. By the early 1990s, six states had enacted laws designed to curb or prohibit the spread of genetically engineered products in the marketplace (see Ill. Ann. Stat. ch. 430, § 95/1 [Smith-Hurd 1995] Me. Rev. Stat. Ann. tit. 7, § 231 et seq. [West 1995] Minn. Stat. Ann. § 116C.91 et seq. [West 1995] N.C. Gen. Stat. § 106-765-780 [Supp. 1991] Okla. Stat. Ann. tit. 2, §§ 2011� [West 1996] Wis. Stat. Ann. § 146.60 [West 1996]). North Carolina's law sets the most comprehensive restrictions on genetic engineering. Resembling the earlier measures proposed by organizations such as England's Genetic Manipulation Advisory Group, it requires scientists to hold a permit for any release of a genetically engineered product out-side a closed-containment enclosure. The North Carolina statute has been cited as a possible model for advocates of comprehensive federal regulations.

Recent Developments

In the mid 1990s the international guidelines established by the Declaration of Helsinki were modified to allow certain forms of cell manipulation in order to develop germ cells for therapeutic purposes. Scientists are also exploring genetic engineering as a means of combating the HIV virus.

In 1997 the cloning of an adult sheep by Scottish scientist Ian Wilmut brought new urgency to the cloning issue. Prior to this development, cloning had been successful only with immature cells, not those from an adult animal. The breakthrough raised the prospect of human cloning and prompted an international debate regarding the ethical and legal implications of cloning.

Since the cloning of the sheep, nicknamed "Dolly," scientists have found the process of cloning to be more difficult than expected. Since Dolly, scientists have cloned such animals as cows, pigs, monkeys, cats, and even rare and endangered animals. The process of cloning is complex, involving the replacement of the nucleus of an egg cell with the nucleus of a cell from the subject that will be cloned. This process is meticulous, and the failure rate is high.

In November 2001, scientists first successfully inserted the DNA from one human cell into another human egg. Although the eggs began to replicate, they died shortly after the procedure. Human cloning has caused the most intense debate on the issue, with the debate focusing upon scientific, moral, and religious concerns over this possibility. Scientists do not expect that human cloning will be possible for several years.

Evidence suggests that cloned animals have experienced significant health problems, leading to concerns about the vitality of the entire process. Cloned animals tend to be larger at birth, which could cause problems for the female animals giving birth to them. The cloned organisms also tend to become obese at middle age, at least in the case of experimental cloned mice. Moreover, evidence suggests that cloned animals have died because they do not have sufficient Immunity defenses to fight disease.

Dolly lived for six years before dying in February 2003, which is about half of the normal life expectancy of a sheep. Proponents of the cloning experiments suggest that cloning opens a number of possibilities in scientific research, including the nature of certain diseases and the development of genetically-enhanced medications. Scientists have also successfully cloned endangered animals. In 2001, an Italian group cloned an endangered form of sheep, called the European mouflon. About a year and a half earlier, an American company, Advanced Cell Technology, tried unsuccessfully to clone a rare Asian ox. The cloning was initially successful, but the animal died of dysentery 48 hours after birth.

In 2000, a group of 138 countries, including the United States, approved the Cartagena Protocol on Biosafety Environment. International concerns over the handling of genetically modified organisms (GMOs) prompted the passage of the protocol. It governs such issues as the safe transfer, handling, use, and disposals of GMOs among member countries.

Further readings

Beauchamp, Tom L., and James F. Childress. 1983. Principles of Biomedical Ethics. New York: Oxford Univ. Pritisnite.

Darvall, Leanna. 1993. Medicine, Law, and Social Change. Aldershot, England Brookfield, Wis.: Dartmouth.

Harder, Ben. 2002. "Scientific Pitfalls Complicate Cloning Debate." National Geographic.

Mason, John Kenyon, and R. A. McCall-Smith. 1994. Law and Medical Ethics. London: Butterworths.

——. 1987. Butterworths Medico-Legal Encyclopedia. London: Butterworths.

Paley, Eric R. 1993. "Rethinking Utility: The Expediency of Granting Patent Protection to Partial CDNA Sequences." Syracuse Law Review.

Ratnoff and Smith. 1968. "Human Laboratory Animals: Martyrs for Medicine." Fordham Law Review 36.

Smith, George P., II. 1993. Bioethics and the Law. Lanham, Md.: Univ. Press of America.

——. 1981. Genetics, Ethics, and the Law. Gaithersburg, Md.: Associated Faculty Press.


Genetski

Some people can test positive for the virus’s genetic material for months after they get well, and shed no infectious virus.

That cut allows the virus to fuse with the cell membrane and dump its genetic material into the cell.

Even though people probably detest mosquitoes more than moth larvae that can damage broccoli, the fact that the Florida Keys project involves genetic modification still stirs passion.

Gene therapy trials are underway for several different genetic diseases, including sickle cell anemia, at least two different forms of inherited blindness, and Alzheimer’s, among others.

Now, a child who shows up at a hospital with severe mycobacterial infection is tested for these genetic defects and receives injections of interferon gamma.

The genetic material can grow quickly, but are typically riddled with errors or defects.

But a 2011 study of genetic evidence from 30 ethnic groups in India disproved this theory.

Prevalence depends on context, and sometimes unique advantages outweigh the genetic costs.

Cryobanks, which screen for genetic disorders and STDs, cost big bucks see here for some of the charges.

Mitochondrial intervention is the practice of replacing DNA that carries a genetic disease.

The most influential attempt at a genetic classification of the various historical forms of government was that of Aristotle.

On the contrary, taking the genetic view of childhood should give us certain advantages.

Hundreds of thousands of years of genetic weeding-out have produced things that would give even an electronic brain nightmares.

The intellectual nature of man is the same as that of angels who have no genetic connection with us.

He did not employ the comparative and genetic methods to which we owe the chief scientific achievements of the last half-century.


Genetics and Identity

We are probably all familiar with the AncestryDNA advertisement for its genetic testing service in which a man states that he and his family had always thought that they were German. He goes on to explain that he danced in a German dance group and wore lederhosen, until, thanks to AncestryDNA, he found out that, in his words, “We’re not German at all!” 52 percent of his DNA came from Ireland, Wales, and Scotland. Thus, he explains, “I traded in my lederhosen for a kilt.” The ad is amusing and memorable, but it also reflects a disturbing trend in identity politics, namely the assumption that our genetic identity informs our ethnic identity, that it is somehow the essence of who we really are. The implication is that our cultural, social, religious, and political identities are secondary, dependent on our primary genetic identity, and we must bring them into harmony with our “real” selves, which is knowable only through our DNA.

There is nothing wrong or pernicious about having one’s genetic ancestry tested—it can be fun, enlightening, and I am sure that the millions of individuals who have paid for such tests have enjoyed learning about the putative geographic origins of their forbearers. Moreover, advanced genetic tests such as those offered by companies such as 23andMe can even screen for potential susceptibility to genetically transmitted health risks. However, at the same time, promoters of this testing are a bit too eager to equate geographical origin with ethnic origin. As one online advertisement states, “Your AncestryDNA results include information about your ethnicity across 26 regions/ethnicities.” But is a regional identity necessarily an ethnic identity?

The Greek term ethnos, from which our modern ethnic derives, has a long and troubled history. If for Homer, a band of comrades or a group of people living and working together might be termed an ethnos, the word later came to mean more specifically a nation or a people, although this doesn’t help much since the definition of a people or a nation has always been dependent on cultural and normative rather than biological imperatives. The imagined unity of a people could derive from shared customs, language, a common law, and a belief in a common origin, whether or not this origin was factual. In many regions of the world, groups with very different cultural identities inhabit the same geographical areas, maintaining their group identities by policing their social boundaries by social custom and marriage prohibitions. In spite of this, individuals and families often move across these lines, in time changing their identities, merging with other ethnicities, and eventually even adopting the shared sense of a past that unites these groups.

What, if anything, does this have to do with genetics? Certainly, populations living in one place for generations intermarry with each other, not only increasing their cultural sense of distinctiveness, but also creating, through the generations, certain identifiable genetically transmitted characteristics. Specific variations in the genome, termed alleles, become more common in such groups, although most of these would have no perceptible influence on the appearance or behavior of those who bear them. Other genetic variations that determine body build, hair, skin, and eye color are more evident, while some, such as those that influence the ability of adults to digest milk or to withstand certain diseases may be even more significant from an adaptive perspective, if less obvious. But no specific set of genetic similarities determines how an individual or group will be identified—what will be seen as essential in classifying members of a group is ultimately culturally determined. Moreover, cultural and political identities can trump genetic origins. Groups that are very similar genetically may hold vastly different and even hostile cultural identities, while people with divergent genetic origins can share a powerful sense of common identity that is the essence of ethnic consciousness.

And of course stability is not the rule in most of human history. Individuals and groups move about, in search of new opportunities, in wars of conquest and colonization, or conversely fleeing war and famine. As they merge with other populations, they bring new genetic material with the result that genetic admixture is the norm in human societies across the globe.

Migration and admixture can change not only the genetic profile of a region, but the complex and often dramatic act of migration can over time change the self-identity of both the host population and that of the new arrivals. These new identities are not specifically tied to genetic differences. Rather, they result from the introduction of new technologies, cultural traditions, social organizations, and the like, which themselves are changed by new environmental and social circumstances.

This confusion between genetic origin and ethnic identity becomes even more problematic when someone like myself is studying populations in the distant past. Together with an international, interdisciplinary team of geneticists, archaeologists, and historians, we are examining population structures and mobility along the collapsing Danubian frontier of the Roman Empire at the end of antiquity. Our comprehensive genetic analysis of almost all of the individuals buried in the sixth century in a single cemetery in what is now Hungary, for example, shows two groups clearly differentiated by genetic origins. One group, if plotted on a modern European genetic map (the way AncestryDNA or 23andMe traces someone’s genetic origins today) would plot to somewhere in central Europe. A second, more diffuse group is most similar to the modern-day populations of Italy. A similar, comprehensive examination of an Italian cemetery near Turin that dates from a few decades later shows a similar pattern: a central European group is again present, as is another group that, while not a close match to the southern group in Hungary, still would plot to Italy today. Our archaeological analysis of the two cemeteries shows that the differences between these two groups are not limited to genetic origin. In both cases, the individuals who belong to the central European group are buried with distinctive weapons and jewelry, while the southern burials are much simpler and contain no grave goods. This suggests that we are dealing with two populations that had not only different genetic origins, but also distinctive cultural practices, at least in the burial of their dead. Moreover, using innovative algorithms we have been able to uncover the biological kinship uniting individuals in these two cemeteries. Most of the family groups we identify in both cemeteries (some spanning three generations) are within the central European group, and we see no evidence of intermarriage between the two.

Since the sixth century is the period when, according to written sources, the Longobards or Lombards, a Germanic population, invaded and conquered much of Italy from what is today Hungary, and some archaeologists have associated these cemeteries with Lombards based on grave goods, it is tempting to label the group from Central Europe as Lombards. But is this justified? Lombard is, after all, a cultural, not a genetic label. Can we be sure that this population, either in Pannonia or in Italy, would have called themselves Lombards, and would have been recognized as such by their neighbors? It is not so simple. Since at least the fourth century, various Germanic groups had been pressing on the Danubian frontier, at times serving the Roman state and at times attacking and occupying the region. Our sources provide ethnic names for various groups: Rugians, Herules, Suebians, Gepids, as well as Lombards. Their origins, like those in our cemeteries, were likely somewhere in central Europe. Moreover, we read that the Lombards, as they expanded into the region in the early 500s conquered these other groups as well as the local post-Roman population still inhabiting the area. Presumably, the warriors in these societies were absorbed into the Lombard military that marched into and conquered Italy in the later sixth century. Perhaps our central European population, rather than being the newly arrived Lombards, were remnants of these other Germanic populations that had lived in the region for centuries. Of course, even if that is the case, they might have been absorbed in the Lombard kingdom and thus, in some ways might have considered themselves, and been considered by others, as Lombards. But while they may have been Lombard according to some criteria—Lombard law, for example, required that a foreigner seeking to enter the authority of the Lombard king had to accept Lombard law—in other respects, they may have continued to hold a different ethnic identity, perhaps in their religion, language, or cultural traditions. Thus the question “Who were they really?” is not one that can be answered through genetic analysis, no matter how detailed.

We can say even less about the two “southern” groups our analyses have discovered. Were they the local, civilian population in the region? Were they the servants or slaves of the militarized society with whom they were buried? How would they have identified themselves? As Romans, as Pannonians, as Italians? And how would that other population have identified them? As peasants? As slaves? Perhaps their fundamental identity would not have been ethnic at all—perhaps their identity was primarily religious—Christian versus pagan, or orthodox versus Arian. Nothing in their DNA can answer these questions.

Our genomic research can tell us a great deal about differences within populations in the past it illuminates population movements and even suggests coincidences between cultural and biological contours within societies that can help us understand social organization. What it cannot do, just as AncestryDNA cannot do, is inform us about the ways that people in the past identified themselves, that deeply held and powerful conviction, regardless of biology, of who we really are. Nor can it tell us how others might have identified these people in the past. To return to our gentleman in the AncestryDNA commercial, while he may be fascinated by his genetic ancestry, he is no more a Scott than he was a German—whatever his biological origins may be, he is clearly an American, and would be so seen in Edinburgh or in Munich.

Patrick Geary, Andrew W. Mellon Professor in the School of Historical Studies, studies a vast range of topics in medieval history, both chronologically and conceptually—from religiosity and social memory to language, ethnicity, social structure, and political organization. He is leading a major project that studies the migration of European societies north and south of the Alps through the analysis of ancient DNA in Longobard-era cemeteries in Hungary and in Italy.



Komentari:

  1. Ragnar

    Čestitam, ova izvrsna ideja je neophodna samo usput

  2. Tanish

    Šteta, što sada ne mogu izraziti - prisiljen je otići. Ali bit ću pušten - nužno ću napisati da razmišljam o ovom pitanju.

  3. Kajinos

    Bravo, ne varaš :)

  4. Beltane

    Sigurno. Bilo je i sa mnom. Možemo komunicirati na ovu temu. Ovdje ili u PM.



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