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Allellar: Versiyalar orasidagi farq

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#YOʻNALTIRISH[[Allellar]]
'''Allel ('''yun. allelon – bir-birini oʻzaro''')'''{{refn|{{IPAc-en|UK|ˈ|æ|l|iː|l|,_|ə|ˈ|l|iː|l}}; yunoncha ἄλλος ''állos'' — «boshqa» so'zidan olingan}} — DNK molekulasi tarkibidagi ma'lum bir joy yoki lokusda (locus) joylashgan nukleotidlar ketma-ketligining varianti hisoblanadi.<ref>{{kitob manbasi |last=Graur |first=D |date=2016 |title=Molecular and Genome Evolution |publisher=Sinauer Associates, Inc. |place=Sunderland MA (USA)}}</ref>
 
Allellar [[Yakka nukleotid polimorfizmi|yakka nukleotid polimorfizmlari]] (single-nucleotide polymorphisms) orqali bir pozitsiyada farq qilishi mumkin,<ref>{{Jurnal manbasi|last1=Smigielski|first1=Elizabeth M.|last2=Sirotkin|first2=Karl|last3=Ward|first3=Minghong|last4=Sherry|first4=Stephen T.|date=2000-01-01|title=dbSNP: a database of single nucleotide polymorphisms|url=https://archive.org/details/nucleic-acids-research_2000-01-01_28_1/page/352|journal=Nucleic Acids Research|volume=28|issue=1|pages=352–355|issn=0305-1048|pmid=10592272|pmc=102496|doi=10.1093/nar/28.1.352}}</ref> biroq ular bir necha ming asoslar juftigacha bo'lgan insersiyalar (insertions) va delitsiyalarni (deletions) ham o'z ichiga olishi mumkin.<ref>{{Kitob manbasi |date=2012 |chapter=Genetic Terminology |title=Statistical Human Genetics |series=Methods in Molecular Biology |pages=1–9 |doi=10.1007/978-1-61779-555-8_1 |isbn=978-1-61779-554-1 |last1=Elston |first1=Robert |last2=Satagopan |first2=Jaya |last3=Sun |first3=Shuying |volume=850 |issn=1064-3745 |pmc=4450815 |pmid=22307690}}</ref> Aksariyat allellar organizmning xususiyatlarida deyarli o'zgarish hosil qilmaydi, lekin ba'zida turli allellar bakteriyalarda antibiotiklarga chidamlilik, meva pashshalarida rivojlanish mutatsiyalari va odamlarda irsiy kasalliklar kabi turli xil kuzatiladigan fenotipik belgilarga olib kelishi mumkin.
 
Deyarli barcha ko'p hujayrali organizmlar biologik hayot siklining ma'lum bir bosqichida ikki to'plam xromosomaga ega bo'ladi, ya'ni ular [[Diploidlik|diploid]] (diploid) hisoblanadi. Berilgan lokus uchun, agar ikkala xromosoma bir xil allelni saqlasa, ular va organizm ushbu allelga nisbatan [[gomoziota]] (homozygous) deb ataladi. Agar allellar turlicha bo'lsa, organizm ushbu allellarga nisbatan [[geterozigota]] (heterozygous) hisoblanadi. Buning yorqin misoli sifatida [[Gregor Mendel]] tomonidan [[no'xat]] o'simligidagi oq va binafsha gul ranglari bitta genning ikkita alleli natijasi ekanligini kashf etganini keltirish mumkin. Mendelning hozir allellar deb ataladigan kashfiyoti allellarning avlodlarga qanday o'tishini tushunishga yordam beradigan uchta qonunning shakllanishiga olib keldi.<ref>{{Jurnal manbasi|title=Gregor Johann Mendel and the development of modern evolutionary biology|journal=Proceedings of the National Academy of Sciences of the United States of America|date=2022-07-26|issn=1091-6490|pmc=9335310|pmid=35858454|article-number=e2201327119|volume=119|issue=30|doi=10.1073/pnas.2201327119|first1=Nils Chr|last1=Stenseth|first2=Leif|last2=Andersson|first3=Hopi E.|last3=Hoekstra|bibcode=2022PNAS..11901327S|doi-access=free}}</ref>
 
Allellarning ommabop ta'riflari odatda faqat genlar ichidagi turli allellarga tegishli bo'ladi. Masalan, [[ABO qon guruhlari tizimi|ABO qon guruhlari]] (ABO blood grouping) oltita keng tarqalgan allelga ega bo'lgan [[ABO (gen)|ABO geni]] tomonidan boshqariladi. [[Populyatsion genetika]]da (population genetics) deyarli har bir tirik insonning ABO geni bo'yicha fenotipi aynan shu oltita allelning ma'lum bir birikmasidan iborat.<ref>{{jurnal manbasi|vauthors=Seltsam A, Hallensleben M, Kollmann A, Blasczyk R|title=The nature of diversity and diversification at the ABO locus|url=https://archive.org/details/sim_blood_2003-10-15_102_8/page/3034|journal=Blood|volume=102|issue=8|pages=3035–42|date=October 2003|pmid=12829588|doi=10.1182/blood-2003-03-0955|doi-access=free}}</ref><ref>{{jurnal manbasi|vauthors=Ogasawara K, Bannai M, Saitou N, Yabe R, Nakata K, Takenaka M, Fujisawa K, Uchikawa M, Ishikawa Y, Juji T, Tokunaga K|title=Extensive polymorphism of ABO blood group gene: three major lineages of the alleles for the common ABO phenotypes|url=https://archive.org/details/sim_human-genetics_1996-06_97_6/page/776|journal=Human Genetics|volume=97|issue=6|pages=777–83|date=June 1996|pmid=8641696|doi=10.1007/BF02346189|s2cid=12076999}}</ref>
 
== Etimologiyasi ==
«Allel» so'zi «allelomorf» («boshqa shakl», 1900-yillarning boshlarida britaniyalik genetiklar [[Uilyam Beytson]] va [[Edit Rebekka Sonders]] tomonidan kiritilgan atama) so'zining qisqartirilgan shaklidir.<ref>{{veb manbasi |last=Craft |first=Jude |title=Genes and genetics: the language of scientific discovery |work=Genes and genetics |publisher=[[Oxford English Dictionary]] |date=2013 |url=http://public.oed.com/aspects-of-english/shapers-of-english/genes-and-genetics-the-language-of-scientific-discovery/ |access-date=2016-01-14 |archive-date=29 January 2018 |archive-url=https://web.archive.org/web/20180129140501/http://public.oed.com/aspects-of-english/shapers-of-english/genes-and-genetics-the-language-of-scientific-discovery/ |url-status=live}}</ref><ref>Bateson, W. and Saunders, E. R. (1902) "The facts of heredity in the light of Mendel's discovery." Reports to the Evolution Committee of the Royal Society, '''I.''' pp. 125–160</ref> Ushbu atama [[genetika]]ning dastlabki davrlarida turli [[fenotip]]larda aniqlangan va ular orasidagi farqlarni keltirib chiqaradigan [[gen]]ning variant shakllarini tasvirlash uchun ishlatilgan. U [[Yunon tili|yunoncha]] ἀλληλο-, ''allelo-'' prefiksidan kelib chiqqan bo'lib, «o'zaro», «bir-biriga» yoki «bir-biri» degan ma'nolarni anglatadi. Bu so'zning o'zi esa yunoncha ἄλλος, ''allos'' (lotincha ''alius'' so'zi bilan bog'liq) sifatidan olingan bo'lib, «boshqa» degan ma'noni bildiradi.
 
== Dominant yoki retsessiv fenotiplarga olib keladigan allellar ==
{{main|Dominantlik (genetika)}}
Ko'p hollarda, lokusdagi ikkita allel o'rtasidagi genotipik o'zaro ta'sirlarni geterozigota qaysi gomoziotik fenotipga ko'proq o'xshashligiga qarab [[Dominantlik (genetika)|dominant]] (dominant) yoki [[Retsessivlik|retsessiv]] (recessive) deb ta'riflash mumkin. Geterozigota gomoziotalardan biridan farq qilmaydigan hollarda, ifodalangan allel «dominant» fenotipga olib keladigan allel hisoblanadi,<ref name="Essential genetics: A genomics perspective" /><ref name="pmid 28696921">{{jurnal manbasi|date=September 2017|title=ASPsiRNA: A Resource of ASP-siRNAs Having Therapeutic Potential for Human Genetic Disorders and Algorithm for Prediction of Their Inhibitory Efficacy|journal=G3|volume=7|issue=9|pages=2931–2943|doi=10.1534/g3.117.044024|pmid=28696921|doi-access=free|last1=Monga|first1=Isha|last2=Qureshi|first2=Abid|last3=Thakur|first3=Nishant|last4=Gupta|first4=Amit Kumar|last5=Kumar|first5=Manoj|pmc=5592921}}</ref> boshqa allel esa «retsessiv» deb ataladi. Geterozigota holatida dominant allel retsessiv allelning ta'sirini niqoblab, dominant fenotipni yuzaga chiqaradi.<ref>{{Veb manbasi |title=Dominant Traits and Alleles |url=https://www.genome.gov/genetics-glossary/Dominant-Traits-and-Alleles |website=www.genome.gov |access-date=2025-12-01 |language=en}}</ref> Retsessiv allellarning fenotipi organizm ma'lum bir gen bo'yicha gomoziota retsessiv bo'lganda kuzatiladi.<ref>{{Veb manbasi |title=Recessive Traits and Alleles |url=https://www.genome.gov/genetics-glossary/Recessive-Traits-Alleles |website=www.genome.gov |access-date=2025-12-01 |language=en}}</ref> Dominantlik darajasi va shakli turli lokuslarda farq qiladi. Ushbu turdagi o'zaro ta'sir birinchi marta Gregor Mendel tomonidan rasman tasvirlangan. Biroq, ko'plab belgilar ushbu oddiy tasnifga bo'ysunmaydi va fenotiplar [[kodominantlik]] (co-dominance) va [[poligen irsiylanish]] (polygenic inheritance) orqali modellashtiriladi.<ref>{{Veb manbasi |url=https://www.genome.gov/genetics-glossary/Allele |title=Allele |website=Genome.gov |access-date=3 July 2021 |archive-date=28 June 2021 |archive-url=https://web.archive.org/web/20210628215931/https://www.genome.gov/genetics-glossary/Allele |url-status=live}}</ref>
 
[[Yovvoyi tur|«Yovvoyi tur»]] (wild type) alleli atamasi ba'zan organizmlarning, masalan, meva pashshalarining (''[[Drosophila melanogaster]]'') «yovvoyi» populyatsiyalarida uchraydigan odatiy fenotipik belgini belgilovchi allelni tasvirlash uchun ishlatiladi. Tarixan bunday «yovvoyi tur» alleli dominant, keng tarqalgan va normal fenotipga olib keladi deb qaralgan, bunga zid ravishda [[Mutant|«mutant»]] (mutant) allellar retsessiv, kam uchraydigan va ko'pincha zararli fenotiplarga olib keladi deb hisoblangan. Ilgari aksariyat shaxslar ko'p gen lokuslarida «yovvoyi tur» alleli bo'yicha gomoziota deb o'ylangan va har qanday muqobil «mutant» allel ozchilikni tashkil etuvchi «kasallangan» shaxslarda gomoziota shaklida (ko'pincha [[irsiy kasalliklar]] sifatida) yoki ko'proq holatlarda mutant allelning [[Genetik tashuvchi|«tashuvchilari»]] (carriers) bo'lgan geterozigotalarda uchrashi taxmin qilingan. Hozir aksariyat yoki barcha gen lokuslari yuqori darajada polimorfik ekanligi, ularning populyatsiyadan populyatsiyaga o'zgarib turadigan bir nechta allellarga egaligi va irsiy o'zgaruvchanlikning katta qismi aniq fenotipik farqlarni keltirib chiqarmaydigan allellar shaklida yashirin ekanligi e'tirof etilgan. Yovvoyi tur allellari ko'pincha yuqori indeksli plyus belgisi bilan belgilanadi (masalan, ''p'' alleli uchun ''p{{sup|+}}'').<ref>{{kitob manbasi |author=B. A. Pierce |date=2020 |title=Genetics A Conceptual Approach |url=https://archive.org/details/bwb_O9-BCT-690 |edition=7 |publisher=Macmillan |isbn=978-1-319-21680-1 |page=[https://archive.org/details/bwb_O9-BCT-690/page/60 60]}}</ref>
 
== Ko'p allellilik ==
{{multiple image|footer=[[Ko'z rangi]] — bu ''[[OCA2]]'' va ''[[HERC2]]'' kabi [[Poligen|bir nechta gen]] ta'sirida shakllanadigan irsiy belgi. Bir nechta genlarning o'zaro ta'siri va shaxslar orasidagi ushbu genlarning o'zgaruvchanligi («allellar») inson ko'z rangining [[fenotip]]ini aniqlashga yordam beradi. Ko'z rangiga [[kamalak parda]]ning [[pigment]]atsiyasi va kamalak parda [[Kamalak parda stromasi|stromasidagi]] [[Loyqalik|loyqa]] muhit tomonidan yorug'likning [[sochilishi]] chastotasi ta'sir qiladi.|width=140|direction=horizontal|image1=Blue eye 2.jpg|image2=Boje oka.jpg|image3=Hazel eye1.png|image4=Human eye with limbal ring, anterior view.jpg|image5=Lens5.jpg}}
[[Fayl:ABO_blood_type.svg|thumb|[[ABO qon guruhlari tizimi]]da A guruhiga ega inson A-antigenlarini namoyon qiladi va I<sup>A</sup>I<sup>A</sup> yoki I<sup>A</sup>i genotipiga ega bo'lishi mumkin. B guruhiga ega inson B-antigenlarini namoyon qiladi va I<sup>B</sup>I<sup>B</sup> yoki I<sup>B</sup>i genotipiga ega bo'lishi mumkin. AB guruhiga ega inson ham A-, ham B-antigenlarini namoyon qiladi va I<sup>A</sup>I<sup>B</sup> genotipiga ega, hech qanday antigenni namoyon qilmaydigan O guruhli inson esa ii genotipiga ega bo'ladi.]]
Organizmlar populyatsiyasi yoki [[tur]]i odatda har bir lokusda turli shaxslar orasida bir nechta allellarni o'z ichiga oladi. Lokusdagi allel o'zgaruvchanligi mavjud allellar soni ([[Genetik polimorfizm|polimorfizm]]) yoki populyatsiyadagi geterozigotalar ulushi sifatida o'lchanadi. [[Null-allel]] (null allele) — bu genning normal funksiyasiga ega bo'lmagan gen varianti bo'lib, u yo ifodalanmaydi yoki ifodalangan oqsil faol emas.
 
Masalan, odamlardagi [[ABO]] [[qon guruhi]] [[Uglevodlar|uglevod]] [[antigen]]lari uchun gen lokusida,<ref name="OnlineMendelianInheritanceinMan" /> klassik genetika [[qon quyish]] mosligini belgilovchi uchta allelni (I<sup>A</sup>, I<sup>B</sup> va i) tan oladi. Har bir shaxs oltita mumkin bo'lgan [[genotip]]dan biriga ega bo'ladi (I<sup>A</sup>I<sup>A</sup>, I<sup>A</sup>i, I<sup>B</sup>I<sup>B</sup>, I<sup>B</sup>i, I<sup>A</sup>I<sup>B</sup> va ii), ular to'rtta mumkin bo'lgan fenotipdan birini hosil qiladi: «A guruhi» (I<sup>A</sup>I<sup>A</sup> gomoziota va I<sup>A</sup>i geterozigota genotiplari tomonidan), «B guruhi» (I<sup>B</sup>I<sup>B</sup> gomoziota va I<sup>B</sup>i geterozigota genotiplari tomonidan), «AB guruhi» (I<sup>A</sup>I<sup>B</sup> geterozigota genotipi tomonidan) va «O guruhi» (ii gomoziota genotipi tomonidan). (Hozir ma'lumki, A, B va O allellarining har biri aslida bir xil xususiyatlarga ega oqsillarni ishlab chiqaradigan turli DNK ketma-ketligiga ega bir nechta allellar sinfidir: ABO lokusida 70 dan ortiq allellar ma'lum.<ref name="Sequence variation at the human ABO locus" /> Shunday qilib, «A guruhi» qoniga ega shaxs AO geterozigota, AA gomoziota yoki ikkita turli «A» alleliga ega AA geterozigota bo'lishi mumkin.)
 
== Genotip chastotalari ==
{{main|Allel chastotasi}}
Diploid populyatsiyadagi allellar chastotasidan mos keladigan genotiplar chastotasini bashorat qilish uchun foydalanish mumkin (qarang: [[Xardi-Vaynberg qonuni|Xardi-Vaynberg tamoyili]]). Ikkita allelga ega oddiy model uchun:
 
: <math>p + q=1 \, </math>
 
: <math>p^2 + 2pq + q^2=1 \,</math>
 
bu yerda ''p'' bitta allelning chastotasi, ''q'' esa muqobil allelning chastotasi bo'lib, ularning yig'indisi birga teng bo'lishi shart. Bunda, ''p''<sup>2</sup> populyatsiyaning birinchi allel bo'yicha gomoziota qismi, 2''pq'' geterozigotalar ulushi va ''q''<sup>2</sup> muqobil allel bo'yicha gomoziota qismidir. Agar birinchi allel ikkinchisiga nisbatan dominant bo'lsa, populyatsiyaning dominant fenotipni ko'rsatadigan qismi ''p''<sup>2</sup> + 2''pq'', retsessiv fenotipga ega qismi esa ''q''<sup>2</sup> ni tashkil etadi.<ref>{{Veb manbasi |title=Archived {{!}} Population Genetics and Statistics for Forensic Analysts {{!}} Hardy-Weinberg Principle {{!}} National Institute of Justice |url=https://nij.ojp.gov/nij-hosted-online-training-courses/population-genetics-and-statistics-forensic-analysts/population-theory/hardy-weinberg-principle |website=nij.ojp.gov |access-date=2025-12-01 |language=en}}</ref>
 
Uchta allel holatida:
 
: <math>p + q + r = 1 \, </math> va
 
: <math>p^2 + q^2 + r^2 + 2pq + 2pr + 2qr = 1. \,</math>
 
Diploid lokusdagi ko'p allellar bo'lganda, allellar soni (a) bo'yicha mumkin bo'lgan genotiplar soni (G) quyidagi ifoda orqali beriladi:
 
: <math>G= \frac{a(a+1)}{2}. </math>
 
== Irsiy kasalliklarda allel dominantligi ==
Bir qator [[irsiy kasalliklar]] shaxs bitta genli belgi uchun ikkita retsessiv allelni meros qilib olganida yuzaga keladi. Retsessiv irsiy kasalliklarga [[albinizm]], [[kistoz fibroz]], [[galaktozemiya]], [[fenilketonuriya]] (PKU) va [[Tey–Saks kasalligi]] kiradi.<ref>{{Veb manbasi |title=Content - Health Encyclopedia - University of Rochester Medical Center |url=https://www.urmc.rochester.edu/encyclopedia/content?ContentTypeID=90&ContentID=P02142 |website=www.urmc.rochester.edu |access-date=2025-12-01}}</ref> Boshqa kasalliklar ham retsessiv allellar bilan bog'liq, ammo gen lokusi X xromosomasida joylashganligi sababli, erkaklarda faqat bitta nusxa mavjud (ya'ni ular [[Gemizigotiklik|gemizigotik]] (hemizygous) hisoblanadi), shuning uchun ular ayollarga qaraganda erkaklarda ko'proq uchraydi. Bunga [[Daltonizm|qizil-yashil rang ko'rligi]] va [[X-xromosoma mo'rtligi sindromi]] misol bo'la oladi.<ref>{{Citation |last=Germain |first=Dominique P. |title=General aspects of X-linked diseases |date=2006 |url=http://www.ncbi.nlm.nih.gov/books/NBK11593/ |work=Fabry Disease: Perspectives from 5 Years of FOS |editor-last=Mehta |editor-first=Atul |access-date=2025-12-01 |place=Oxford |publisher=Oxford PharmaGenesis |isbn=978-1-903539-03-3 |pmid=21290690 |editor2-last=Beck |editor2-first=Michael |editor3-last=Sunder-Plassmann |editor3-first=Gere}}</ref>
 
[[Xantington kasalligi]] kabi boshqa buzilishlar shaxs faqat bitta dominant allelni meros qilib olganida yuzaga keladi.<ref>{{Citation |last1=Troiano |first1=André R. |title=Clinical features of early and juvenile onset in polyglutamine disorders other than Huntington's disease: autosomal dominant cerebellar ataxias and dentatorubral pallidoluysian atrophy |date=January 2009 |work=Juvenile Huntington's Disease |pages=118–134 |publisher=Oxford University Press |doi=10.1093/med/9780199236121.003.0008 |isbn=978-0-19-923612-1 |last2=Dürr |first2=Alexandra}}</ref>
 
== Epiallellar ==
[[Irsiylanish|Irsiy belgilar]] odatda genetik allellar nuqtai nazaridan o'rganilsa-da, [[DNK metillanishi]] (DNA methylation) kabi [[Epigenetika|epigenetik]] (epigenetic) belgilar ma'lum turlarda o'ziga xos genomik hududlarda irsiylanishi mumkin, bu jarayon [[Transgeneratsion epigenetik irsiylanish|avlodlararo epigenetik irsiylanish]] deb ataladi. «Epiallel» (epiallele) atamasi ushbu irsiy belgilarni [[nukleotidlar ketma-ketligi]] bilan belgilanadigan an'anaviy allellardan farqlash uchun ishlatiladi.<ref>{{jurnal manbasi|last1=Daxinger|first1=Lucia|last2=Whitelaw|first2=Emma|title=Understanding transgenerational epigenetic inheritance via the gametes in mammals|journal=Nature Reviews Genetics|date=31 January 2012|volume=13|issue=3|pages=153–62|doi=10.1038/nrg3188|pmid=22290458|s2cid=8654616}}</ref> Sichqonlarda va odamlarda epiallellarning o'ziga xos sinfi — [[Metastabil epiallellar]] (metastable epialleles) kashf etilgan bo'lib, ular mitotik tarzda irsiylanishi mumkin bo'lgan epigenetik holatning stoxastik (ehtimoliy) o'rnatilishi bilan tavsiflanadi.<ref>{{jurnal manbasi|last1=Rakyan|first1=Vardhman K|last2=Blewitt|first2=Marnie E|last3=Druker|first3=Riki|last4=Preis|first4=Jost I|last5=Whitelaw|first5=Emma|title=Metastable epialleles in mammals|url=https://archive.org/details/sim_trends-in-genetics_2002-07_18_7/page/348|journal=Trends in Genetics|date=July 2002|volume=18|issue=7|pages=348–351|doi=10.1016/S0168-9525(02)02709-9|pmid=12127774}}</ref><ref>{{jurnal manbasi|last1=Waterland|first1=RA|last2=Dolinoy|first2=DC|last3=Lin|first3=JR|last4=Smith|first4=CA|last5=Shi|first5=X|last6=Tahiliani|first6=KG|title=Maternal methyl supplements increase offspring DNA methylation at Axin Fused.|journal=Genesis|date=September 2006|volume=44|issue=9|pages=401–6|pmid=16868943|doi=10.1002/dvg.20230|s2cid=36938621}}</ref>
 
== Idiomorf ==
Yunoncha «morphos» (shakl) va «idio» (o'ziga xos, noyob) so'zlaridan olingan «idiomorf» (idiomorph) atamasi 1990-yilda «allel» o'rniga turli shtammlardagi bir xil lokusda joylashgan, ketma-ketlik o'xshashligi bo'lmagan va ehtimol umumiy filogenetik munosabatga ega bo'lmagan ketma-ketliklarni belgilash uchun kiritilgan. U asosan [[mikologiya]] sohasidagi genetik tadqiqotlarda qo'llaniladi.<ref>{{Jurnal manbasi|doi=10.1093/genetics/132.1.125|doi-access=free|pmc=1205111|pmid=1398049|title=Isolation of Neurospora crassa a mating type mutants by repeat induced point (RIP) mutation|url=https://archive.org/details/sim_genetics_1992-09_132_1/page/124|year=1992|last1=Glass|first1=N. L.|last2=Lee|first2=L.|journal=Genetics|volume=132|pages=125–133}}</ref><ref>{{Jurnal manbasi|doi=10.1002/bies.950120202|title=Mating type and mating strategies in ''Neurospora''|url=https://archive.org/details/sim_bioessays_1990-02_12_2/page/n53|year=1990|last1=Metzenberg|first1=Robert L.|last2=Glass|first2=N. Louise|journal=BioEssays|volume=12|issue=2|pages=53–59|pmid=2140508|bibcode=1990BiEss..12...53M|s2cid=10818930}}</ref>
{{Portal|Evolyutsion biologiya
}}
 
== Manbalar ==
{{Manbalar|refs=<ref name="OnlineMendelianInheritanceinMan">{{veb manbasi|url=https://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=110300 |title=ABO Glycosyltransferase; ABO |author1=Victor A. McKusick |author2=Cassandra L. Kniffin |author3=Paul J. Converse |author4=Ada Hamosh |date=10 November 2009 |work=Online Mendelian Inheritance in Man |publisher=National Library of Medicine |access-date=24 March 2010 |archive-url=https://web.archive.org/web/20080924220935/http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=110300 |archive-date=24 September 2008 }}</ref><ref name="Essential genetics: A genomics perspective">{{kitob manbasi |title=Essential genetics: A genomics perspective |url=https://archive.org/details/essentialgenetic0004edhart_v9w2 |edition=4th |last=Hartl |first=Daniel L. |author2=Elizabeth W. Jones |year=2005 |publisher=Jones & Bartlett Publishers |isbn=978-0-7637-3527-2 |page=[https://archive.org/details/essentialgenetic0004edhart_v9w2/page/600 600] }}<!--|access-date=5 October 2009--></ref><ref name="Sequence variation at the human ABO locus">{{jurnal manbasi |author=Yip SP |title=Sequence variation at the human ABO locus |journal=Annals of Human Genetics |volume=66 |issue=1 |pages=1–27 |date=January 2002 |pmid=12014997 |doi=10.1017/S0003480001008995|doi-access=free }}</ref>}}<ref>{{Jurnal manbasi|title=What can we learn from selfish loci that break Mendel's law?|journal=PLOS Biology|date=2022-07-19|issn=1545-7885|pmc=9295977|pmid=35853012|article-number=e3001700|volume=20|issue=7|doi=10.1371/journal.pbio.3001700|language=en|first=Sarah E.|last=Zanders|doi-access=free}}</ref>
 
== Tashqi havolalar ==
{{Wiktionary|allele}}
 
* [http://alfred.med.yale.edu/alfred/index.asp ALFRED: Allellar chastotasi ma'lumotlar bazasi] {{Webarxiv|url=https://web.archive.org/web/20111102214252/http://alfred.med.yale.edu/alfred/index.asp |date=2011-11-02 }}

$2, $3 dagi (joriy) koʻrinishi

Allel (yun. allelon – bir-birini oʻzaro)[1] — DNK molekulasi tarkibidagi ma'lum bir joy yoki lokusda (locus) joylashgan nukleotidlar ketma-ketligining varianti hisoblanadi.[2]

Allellar yakka nukleotid polimorfizmlari (single-nucleotide polymorphisms) orqali bir pozitsiyada farq qilishi mumkin,[3] biroq ular bir necha ming asoslar juftigacha bo'lgan insersiyalar (insertions) va delitsiyalarni (deletions) ham o'z ichiga olishi mumkin.[4] Aksariyat allellar organizmning xususiyatlarida deyarli o'zgarish hosil qilmaydi, lekin ba'zida turli allellar bakteriyalarda antibiotiklarga chidamlilik, meva pashshalarida rivojlanish mutatsiyalari va odamlarda irsiy kasalliklar kabi turli xil kuzatiladigan fenotipik belgilarga olib kelishi mumkin.

Deyarli barcha ko'p hujayrali organizmlar biologik hayot siklining ma'lum bir bosqichida ikki to'plam xromosomaga ega bo'ladi, ya'ni ular diploid (diploid) hisoblanadi. Berilgan lokus uchun, agar ikkala xromosoma bir xil allelni saqlasa, ular va organizm ushbu allelga nisbatan gomoziota (homozygous) deb ataladi. Agar allellar turlicha bo'lsa, organizm ushbu allellarga nisbatan geterozigota (heterozygous) hisoblanadi. Buning yorqin misoli sifatida Gregor Mendel tomonidan no'xat o'simligidagi oq va binafsha gul ranglari bitta genning ikkita alleli natijasi ekanligini kashf etganini keltirish mumkin. Mendelning hozir allellar deb ataladigan kashfiyoti allellarning avlodlarga qanday o'tishini tushunishga yordam beradigan uchta qonunning shakllanishiga olib keldi.[5]

Allellarning ommabop ta'riflari odatda faqat genlar ichidagi turli allellarga tegishli bo'ladi. Masalan, ABO qon guruhlari (ABO blood grouping) oltita keng tarqalgan allelga ega bo'lgan ABO geni tomonidan boshqariladi. Populyatsion genetikada (population genetics) deyarli har bir tirik insonning ABO geni bo'yicha fenotipi aynan shu oltita allelning ma'lum bir birikmasidan iborat.[6][7]

Etimologiyasi

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«Allel» so'zi «allelomorf» («boshqa shakl», 1900-yillarning boshlarida britaniyalik genetiklar Uilyam Beytson va Edit Rebekka Sonders tomonidan kiritilgan atama) so'zining qisqartirilgan shaklidir.[8][9] Ushbu atama genetikaning dastlabki davrlarida turli fenotiplarda aniqlangan va ular orasidagi farqlarni keltirib chiqaradigan genning variant shakllarini tasvirlash uchun ishlatilgan. U yunoncha ἀλληλο-, allelo- prefiksidan kelib chiqqan bo'lib, «o'zaro», «bir-biriga» yoki «bir-biri» degan ma'nolarni anglatadi. Bu so'zning o'zi esa yunoncha ἄλλος, allos (lotincha alius so'zi bilan bog'liq) sifatidan olingan bo'lib, «boshqa» degan ma'noni bildiradi.

Dominant yoki retsessiv fenotiplarga olib keladigan allellar

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Asosiy maqola: Dominantlik (genetika)

Ko'p hollarda, lokusdagi ikkita allel o'rtasidagi genotipik o'zaro ta'sirlarni geterozigota qaysi gomoziotik fenotipga ko'proq o'xshashligiga qarab dominant (dominant) yoki retsessiv (recessive) deb ta'riflash mumkin. Geterozigota gomoziotalardan biridan farq qilmaydigan hollarda, ifodalangan allel «dominant» fenotipga olib keladigan allel hisoblanadi,[10][11] boshqa allel esa «retsessiv» deb ataladi. Geterozigota holatida dominant allel retsessiv allelning ta'sirini niqoblab, dominant fenotipni yuzaga chiqaradi.[12] Retsessiv allellarning fenotipi organizm ma'lum bir gen bo'yicha gomoziota retsessiv bo'lganda kuzatiladi.[13] Dominantlik darajasi va shakli turli lokuslarda farq qiladi. Ushbu turdagi o'zaro ta'sir birinchi marta Gregor Mendel tomonidan rasman tasvirlangan. Biroq, ko'plab belgilar ushbu oddiy tasnifga bo'ysunmaydi va fenotiplar kodominantlik (co-dominance) va poligen irsiylanish (polygenic inheritance) orqali modellashtiriladi.[14]

«Yovvoyi tur» (wild type) alleli atamasi ba'zan organizmlarning, masalan, meva pashshalarining (Drosophila melanogaster) «yovvoyi» populyatsiyalarida uchraydigan odatiy fenotipik belgini belgilovchi allelni tasvirlash uchun ishlatiladi. Tarixan bunday «yovvoyi tur» alleli dominant, keng tarqalgan va normal fenotipga olib keladi deb qaralgan, bunga zid ravishda «mutant» (mutant) allellar retsessiv, kam uchraydigan va ko'pincha zararli fenotiplarga olib keladi deb hisoblangan. Ilgari aksariyat shaxslar ko'p gen lokuslarida «yovvoyi tur» alleli bo'yicha gomoziota deb o'ylangan va har qanday muqobil «mutant» allel ozchilikni tashkil etuvchi «kasallangan» shaxslarda gomoziota shaklida (ko'pincha irsiy kasalliklar sifatida) yoki ko'proq holatlarda mutant allelning «tashuvchilari» (carriers) bo'lgan geterozigotalarda uchrashi taxmin qilingan. Hozir aksariyat yoki barcha gen lokuslari yuqori darajada polimorfik ekanligi, ularning populyatsiyadan populyatsiyaga o'zgarib turadigan bir nechta allellarga egaligi va irsiy o'zgaruvchanlikning katta qismi aniq fenotipik farqlarni keltirib chiqarmaydigan allellar shaklida yashirin ekanligi e'tirof etilgan. Yovvoyi tur allellari ko'pincha yuqori indeksli plyus belgisi bilan belgilanadi (masalan, p alleli uchun p+).[15]

Ko'p allellilik

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Ko'z rangi — bu OCA2 va HERC2 kabi bir nechta gen ta'sirida shakllanadigan irsiy belgi. Bir nechta genlarning o'zaro ta'siri va shaxslar orasidagi ushbu genlarning o'zgaruvchanligi («allellar») inson ko'z rangining fenotipini aniqlashga yordam beradi. Ko'z rangiga kamalak pardaning pigmentatsiyasi va kamalak parda stromasidagi loyqa muhit tomonidan yorug'likning sochilishi chastotasi ta'sir qiladi.
ABO qon guruhlari tizimida A guruhiga ega inson A-antigenlarini namoyon qiladi va IAIA yoki IAi genotipiga ega bo'lishi mumkin. B guruhiga ega inson B-antigenlarini namoyon qiladi va IBIB yoki IBi genotipiga ega bo'lishi mumkin. AB guruhiga ega inson ham A-, ham B-antigenlarini namoyon qiladi va IAIB genotipiga ega, hech qanday antigenni namoyon qilmaydigan O guruhli inson esa ii genotipiga ega bo'ladi.

Organizmlar populyatsiyasi yoki turi odatda har bir lokusda turli shaxslar orasida bir nechta allellarni o'z ichiga oladi. Lokusdagi allel o'zgaruvchanligi mavjud allellar soni (polimorfizm) yoki populyatsiyadagi geterozigotalar ulushi sifatida o'lchanadi. Null-allel (null allele) — bu genning normal funksiyasiga ega bo'lmagan gen varianti bo'lib, u yo ifodalanmaydi yoki ifodalangan oqsil faol emas.

Masalan, odamlardagi ABO qon guruhi uglevod antigenlari uchun gen lokusida,[16] klassik genetika qon quyish mosligini belgilovchi uchta allelni (IA, IB va i) tan oladi. Har bir shaxs oltita mumkin bo'lgan genotipdan biriga ega bo'ladi (IAIA, IAi, IBIB, IBi, IAIB va ii), ular to'rtta mumkin bo'lgan fenotipdan birini hosil qiladi: «A guruhi» (IAIA gomoziota va IAi geterozigota genotiplari tomonidan), «B guruhi» (IBIB gomoziota va IBi geterozigota genotiplari tomonidan), «AB guruhi» (IAIB geterozigota genotipi tomonidan) va «O guruhi» (ii gomoziota genotipi tomonidan). (Hozir ma'lumki, A, B va O allellarining har biri aslida bir xil xususiyatlarga ega oqsillarni ishlab chiqaradigan turli DNK ketma-ketligiga ega bir nechta allellar sinfidir: ABO lokusida 70 dan ortiq allellar ma'lum.[17] Shunday qilib, «A guruhi» qoniga ega shaxs AO geterozigota, AA gomoziota yoki ikkita turli «A» alleliga ega AA geterozigota bo'lishi mumkin.)

Genotip chastotalari

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Asosiy maqola: Allel chastotasi

Diploid populyatsiyadagi allellar chastotasidan mos keladigan genotiplar chastotasini bashorat qilish uchun foydalanish mumkin (qarang: Xardi-Vaynberg tamoyili). Ikkita allelga ega oddiy model uchun:

p+q=1{\displaystyle p + q=1 \,}
p2+2pq+q2=1{\displaystyle p^2 + 2pq + q^2=1 \,}

bu yerda p bitta allelning chastotasi, q esa muqobil allelning chastotasi bo'lib, ularning yig'indisi birga teng bo'lishi shart. Bunda, p2 populyatsiyaning birinchi allel bo'yicha gomoziota qismi, 2pq geterozigotalar ulushi va q2 muqobil allel bo'yicha gomoziota qismidir. Agar birinchi allel ikkinchisiga nisbatan dominant bo'lsa, populyatsiyaning dominant fenotipni ko'rsatadigan qismi p2 + 2pq, retsessiv fenotipga ega qismi esa q2 ni tashkil etadi.[18]

Uchta allel holatida:

p+q+r=1{\displaystyle p + q + r = 1 \,} va
p2+q2+r2+2pq+2pr+2qr=1.{\displaystyle p^2 + q^2 + r^2 + 2pq + 2pr + 2qr = 1. \,}

Diploid lokusdagi ko'p allellar bo'lganda, allellar soni (a) bo'yicha mumkin bo'lgan genotiplar soni (G) quyidagi ifoda orqali beriladi:

G=a(a+1)2.{\displaystyle G= \frac{a(a+1)}{2}.}

Irsiy kasalliklarda allel dominantligi

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Bir qator irsiy kasalliklar shaxs bitta genli belgi uchun ikkita retsessiv allelni meros qilib olganida yuzaga keladi. Retsessiv irsiy kasalliklarga albinizm, kistoz fibroz, galaktozemiya, fenilketonuriya (PKU) va Tey–Saks kasalligi kiradi.[19] Boshqa kasalliklar ham retsessiv allellar bilan bog'liq, ammo gen lokusi X xromosomasida joylashganligi sababli, erkaklarda faqat bitta nusxa mavjud (ya'ni ular gemizigotik (hemizygous) hisoblanadi), shuning uchun ular ayollarga qaraganda erkaklarda ko'proq uchraydi. Bunga qizil-yashil rang ko'rligi va X-xromosoma mo'rtligi sindromi misol bo'la oladi.[20]

Xantington kasalligi kabi boshqa buzilishlar shaxs faqat bitta dominant allelni meros qilib olganida yuzaga keladi.[21]

Epiallellar

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Irsiy belgilar odatda genetik allellar nuqtai nazaridan o'rganilsa-da, DNK metillanishi (DNA methylation) kabi epigenetik (epigenetic) belgilar ma'lum turlarda o'ziga xos genomik hududlarda irsiylanishi mumkin, bu jarayon avlodlararo epigenetik irsiylanish deb ataladi. «Epiallel» (epiallele) atamasi ushbu irsiy belgilarni nukleotidlar ketma-ketligi bilan belgilanadigan an'anaviy allellardan farqlash uchun ishlatiladi.[22] Sichqonlarda va odamlarda epiallellarning o'ziga xos sinfi — Metastabil epiallellar (metastable epialleles) kashf etilgan bo'lib, ular mitotik tarzda irsiylanishi mumkin bo'lgan epigenetik holatning stoxastik (ehtimoliy) o'rnatilishi bilan tavsiflanadi.[23][24]

Idiomorf

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Yunoncha «morphos» (shakl) va «idio» (o'ziga xos, noyob) so'zlaridan olingan «idiomorf» (idiomorph) atamasi 1990-yilda «allel» o'rniga turli shtammlardagi bir xil lokusda joylashgan, ketma-ketlik o'xshashligi bo'lmagan va ehtimol umumiy filogenetik munosabatga ega bo'lmagan ketma-ketliklarni belgilash uchun kiritilgan. U asosan mikologiya sohasidagi genetik tadqiqotlarda qo'llaniladi.[25][26]

Manbalar

[tahrir | manbasini tahrirlash]
  1. ↑ BB: /ˈæliːl, əˈliːl/; yunoncha ἄλλος állos — «boshqa» so'zidan olingan
  2. ↑ Graur, D. Molecular and Genome Evolution. Sinauer Associates, Inc., 2016. 
  3. ↑ Smigielski, Elizabeth M.; Sirotkin, Karl; Ward, Minghong; Sherry, Stephen T. (2000-01-01). „dbSNP: a database of single nucleotide polymorphisms“. Nucleic Acids Research. 28-jild, № 1. 352–355-bet. doi:10.1093/nar/28.1.352. ISSN 0305-1048. PMC 102496. PMID 10592272.
  4. ↑ Elston, Robert; Satagopan, Jaya; Sun, Shuying „Genetic Terminology“, . Statistical Human Genetics, Methods in Molecular Biology, 2012 — 1–9-bet. DOI:10.1007/978-1-61779-555-8_1. ISBN 978-1-61779-554-1. 
  5. ↑ Stenseth, Nils Chr; Andersson, Leif; Hoekstra, Hopi E. (2022-07-26). „Gregor Johann Mendel and the development of modern evolutionary biology“. Proceedings of the National Academy of Sciences of the United States of America. 119-jild, № 30. Bibcode:2022PNAS..11901327S. doi:10.1073/pnas.2201327119. ISSN 1091-6490. PMC 9335310. PMID 35858454. {{cite magazine}}: Unknown parameter |article-number= ignored (yordam)
  6. ↑ Seltsam A, Hallensleben M, Kollmann A, Blasczyk R (October 2003). „The nature of diversity and diversification at the ABO locus“. Blood. 102-jild, № 8. 3035–42-bet. doi:10.1182/blood-2003-03-0955. PMID 12829588.
  7. ↑ Ogasawara K, Bannai M, Saitou N, Yabe R, Nakata K, Takenaka M, Fujisawa K, Uchikawa M, Ishikawa Y, Juji T, Tokunaga K (June 1996). „Extensive polymorphism of ABO blood group gene: three major lineages of the alleles for the common ABO phenotypes“. Human Genetics. 97-jild, № 6. 777–83-bet. doi:10.1007/BF02346189. PMID 8641696. S2CID 12076999.
  8. ↑ Craft, Jude „Genes and genetics: the language of scientific discovery“. Genes and genetics. Oxford English Dictionary (2013). 2018-yil 29-yanvarda asl nusxadan arxivlangan. Qaraldi: 2016-yil 14-yanvar.
  9. ↑ Bateson, W. and Saunders, E. R. (1902) "The facts of heredity in the light of Mendel's discovery." Reports to the Evolution Committee of the Royal Society, I. pp. 125–160
  10. ↑ Hartl, Daniel L.; Elizabeth W. Jones. Essential genetics: A genomics perspective, 4th, Jones & Bartlett Publishers, 2005 — 600-bet. ISBN 978-0-7637-3527-2. 
  11. ↑ Monga, Isha; Qureshi, Abid; Thakur, Nishant; Gupta, Amit Kumar; Kumar, Manoj (September 2017). „ASPsiRNA: A Resource of ASP-siRNAs Having Therapeutic Potential for Human Genetic Disorders and Algorithm for Prediction of Their Inhibitory Efficacy“. G3. 7-jild, № 9. 2931–2943-bet. doi:10.1534/g3.117.044024. PMC 5592921. PMID 28696921.
  12. ↑ „Dominant Traits and Alleles“ (en). www.genome.gov. Qaraldi: 2025-yil 1-dekabr.
  13. ↑ „Recessive Traits and Alleles“ (en). www.genome.gov. Qaraldi: 2025-yil 1-dekabr.
  14. ↑ „Allele“. Genome.gov. 2021-yil 28-iyunda asl nusxadan arxivlangan. Qaraldi: 2021-yil 3-iyul.
  15. ↑ B. A. Pierce. Genetics A Conceptual Approach, 7, Macmillan, 2020 — 60-bet. ISBN 978-1-319-21680-1. 
  16. ↑ Victor A. McKusick; Cassandra L. Kniffin; Paul J. Converse; Ada Hamosh „ABO Glycosyltransferase; ABO“. Online Mendelian Inheritance in Man. National Library of Medicine (2009-yil 10-noyabr). 2008-yil 24-sentyabrda asl nusxadan arxivlangan. Qaraldi: 2010-yil 24-mart.
  17. ↑ Yip SP (January 2002). „Sequence variation at the human ABO locus“. Annals of Human Genetics. 66-jild, № 1. 1–27-bet. doi:10.1017/S0003480001008995. PMID 12014997.
  18. ↑ „Archived | Population Genetics and Statistics for Forensic Analysts | Hardy-Weinberg Principle | National Institute of Justice“ (en). nij.ojp.gov. Qaraldi: 2025-yil 1-dekabr.
  19. ↑ „Content - Health Encyclopedia - University of Rochester Medical Center“. www.urmc.rochester.edu. Qaraldi: 2025-yil 1-dekabr.
  20. ↑ Germain, Dominique P. (2006), Mehta, Atul; Beck, Michael; Sunder-Plassmann, Gere (muh.), „General aspects of X-linked diseases“, Fabry Disease: Perspectives from 5 Years of FOS, Oxford: Oxford PharmaGenesis, ISBN 978-1-903539-03-3, PMID 21290690, qaraldi: 2025-12-01
  21. ↑ Troiano, André R.; Dürr, Alexandra (January 2009), „Clinical features of early and juvenile onset in polyglutamine disorders other than Huntington's disease: autosomal dominant cerebellar ataxias and dentatorubral pallidoluysian atrophy“, Juvenile Huntington's Disease, Oxford University Press, 118–134-bet, doi:10.1093/med/9780199236121.003.0008, ISBN 978-0-19-923612-1
  22. ↑ Daxinger, Lucia; Whitelaw, Emma (31 January 2012). „Understanding transgenerational epigenetic inheritance via the gametes in mammals“. Nature Reviews Genetics. 13-jild, № 3. 153–62-bet. doi:10.1038/nrg3188. PMID 22290458. S2CID 8654616.
  23. ↑ Rakyan, Vardhman K; Blewitt, Marnie E; Druker, Riki; Preis, Jost I; Whitelaw, Emma (July 2002). „Metastable epialleles in mammals“. Trends in Genetics. 18-jild, № 7. 348–351-bet. doi:10.1016/S0168-9525(02)02709-9. PMID 12127774.
  24. ↑ Waterland, RA; Dolinoy, DC; Lin, JR; Smith, CA; Shi, X; Tahiliani, KG (September 2006). „Maternal methyl supplements increase offspring DNA methylation at Axin Fused“. Genesis. 44-jild, № 9. 401–6-bet. doi:10.1002/dvg.20230. PMID 16868943. S2CID 36938621.
  25. ↑ Glass, N. L.; Lee, L. (1992). „Isolation of Neurospora crassa a mating type mutants by repeat induced point (RIP) mutation“. Genetics. 132-jild. 125–133-bet. doi:10.1093/genetics/132.1.125. PMC 1205111. PMID 1398049.
  26. ↑ Metzenberg, Robert L.; Glass, N. Louise (1990). „Mating type and mating strategies in Neurospora“. BioEssays. 12-jild, № 2. 53–59-bet. Bibcode:1990BiEss..12...53M. doi:10.1002/bies.950120202. PMID 2140508. S2CID 10818930.

[1]

Tashqi havolalar

[tahrir | manbasini tahrirlash]
Vikilugʻatda allele nomli maqola mavjud.


  1. ↑ Zanders, Sarah E. (2022-07-19). „What can we learn from selfish loci that break Mendel's law?“. PLOS Biology (inglizcha). 20-jild, № 7. doi:10.1371/journal.pbio.3001700. ISSN 1545-7885. PMC 9295977. PMID 35853012. {{cite magazine}}: Unknown parameter |article-number= ignored (yordam) 
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