Kontent qismiga oʻtish

Hujayrasiz hayot

Vikipediya, erkin ensiklopediya
Virus.

Hujayrasiz hayot (non-cellular life yoki acellular life) — o'z hayot siklining (life cycle) kamida bir qismida hujayraviy (cellular) tuzilishga ega bo'lmagan hayot shaklidir.[1] Tarixan hayotga berilgan aksariyat ta'riflarda organizm bir yoki bir nechta hujayradan tashkil topishi lozimligi ta'kidlangan,[2] biroq ba'zi olimlar uchun bu endi zaruriy shart hisoblanmaydi va zamonaviy mezonlar boshqa tizimli tuzilmalarga asoslangan hayot shakllarini tan olish imkonini beradi.[3][4][5]

Nuklein kislota saqlovchi yuqumli agentlar

[tahrir | manbasini tahrirlash]

Viruslar

[tahrir | manbasini tahrirlash]
virus turlarini ko'rsatuvchi tasvir
Virus turlari

Tadqiqotchilar dastlab viruslarni «zahar» (poison) yoki «toksin» (toxin), so'ngra «yuqumli oqsillar» (infectious proteins) sifatida ta'riflashgan; biroq ular genetik materialga, aniq tuzilishga va o'z tarkibiy qismlaridan mustaqil ravishda yig'ilish qobiliyatiga ega. Bu ularni tubdan biokimyoviy molekulalar yoki juda kichik biologik organizmlar deb hisoblash kerakligi borasida keng ko'lamli munozaralarga sabab bo'ldi. Xo'jayin hujayrasiz ular hayotning hech bir funksiyasini — masalan, metabolizm (metabolism), o'sish yoki ko'payishni amalga oshira olmaydi. 1950-yillardan boshlab ko'plab olimlar viruslarni kimyo va hayot o'rtasidagi chegara, ya'ni tiriklik va jonsizlik orasidagi «kulrang hudud» sifatida ko'ra boshladilar.[6][7][8]

Viroidlar

[tahrir | manbasini tahrirlash]
Asosiy maqola: Viroid

Agar viruslar chegara holatlari yoki jonsiz deb hisoblansa, viroidlar (viroid) tirik organizm bo'lishdan yanada yiroqdir. Viroidlar oqsil qobig'iga ega bo'lmagan, faqatgina bitta zanjirli halqasimon RNK qismlaridan tashkil topgan eng kichik yuqumli agentlardir. Ularning faqat gulli o'simliklarni zararlashi ma'lum bo'lib, ulardan ba'zilari tijorat ahamiyatiga ega. Viroid genomlari (genome) o'lchami 246 dan 467 gacha nukleotid asoslaridan (nucleobases) iborat bo'lib, juda kichikdir. Taqqoslash uchun, infeksiya qo'zg'atishga qodir bo'lgan eng kichik viruslarning genomi taxminan 2000 nukleotiddan tashkil topgan.[9][10] Viroid RNKsi hech qanday oqsilni kodlamaydi.[11] Uning replikatsiyasi (replication) mexanizmi RNK-polimeraza II (RNA polymerase II) — odatda DNKdan informatsion RNK sintez qilish bilan bog'liq bo'lgan xo'jayin hujayra fermentini «o'g'irlab» oladi. Buning o'rniga ferment viroid RNKsidan qolip sifatida foydalanib, «aylanma halqa» (rolling circle) usulida yangi RNK sintezini katalizlaydi. Ba'zi viroidlar ribozimlar (ribozymes) bo'lib, ular o'z-o'zini kesish va katta replikatsiya oraliq mahsulotlaridan birlik o'lchamdagi genomlarni bog'lash imkonini beruvchi katalitik xususiyatlarga ega.[12]

Viroidlarning kelib chiqishi ularni DNK yoki oqsil evolyutsiyasidan oldingi faraziy, qadimiy va hujayrasiz RNK dunyosining (RNA world) «tirik qoldiqlari» sifatida ko'rish bilan izohlanishi mumkin.[13][14] 1980-yillarda ilgari surilgan ushbu qarash 2010-yillarda hayotning jonsiz moddadan (abiogenez) evolyutsiyasidagi muhim oraliq bosqichlarni tushuntirish uchun qayta ommalashdi.[15][16]

Obelisklar

[tahrir | manbasini tahrirlash]
Asosiy maqola: Obelisk (biologiya)

2024-yilda tadqiqotchilar obelisklar (obelisks) deb nomlangan viroidsimon, ammo alohida RNKga asoslangan elementlarning ehtimoliy kashfiyotini e'lon qildilar. Inson mikrobiomasi (microbiome) ma'lumotlar bazalarida topilgan obelisklar, ehtimol, ichak bakteriyalarida yashaydi. Ular viroidlardan ikki xil alohida oqsillarni («oblinlar») kodlashi va RNKsining tayoqchasimon ikkilamchi tuzilishi bilan farq qiladi.[17][18]

Birinchi universal umumiy ajdod

[tahrir | manbasini tahrirlash]

Birinchi universal umumiy ajdod (first universal common ancestor — FUCA) taklif etilayotgan hujayrasiz hayot shakliga misol bo'la oladi. Chunki u oxirgi universal umumiy ajdod (last universal common ancestor — LUCA), uning qardosh tarmoqlari va hozirgi vaqtda yashayotgan har bir hujayraning eng qadimgi ajdodi hisoblanadi.[19]

Yana qarang

[tahrir | manbasini tahrirlash]

Manbalar

[tahrir | manbasini tahrirlash]
  1. ↑ „What is Non-Cellular Life?“. Wise Geek. Conjecture Corporation (2009). 2021-yil 21-yanvarda asl nusxadan arxivlangan. Qaraldi: 2009-yil 2-avgust.
  2. ↑ „The 7 Characteristics of Life“. infohost.nmt.edu. 2016-yil 19-noyabrda asl nusxadan arxivlangan. Qaraldi: 2017-yil 26-yanvar.[yaxshiroq manba kerak]
  3. ↑ Benner, Steven A. (2017-01-26). "Defining Life". Astrobiology 10 (10): 1021–1030. doi:10.1089/ast.2010.0524. ISSN 1531-1074. PMID 21162682. PMC 3005285. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3005285. 
  4. ↑ Trifonov, Edward (2012). "Definition of Life: Navigation through Uncertainties". Journal of Biomolecular Structure & Dynamics 29 (4): 647–650. doi:10.1080/073911012010525017. PMID 22208269. http://www.jbsdonline.com/mc_images/category/4317/21-trifonov-jbsd_29_4_2012.pdf. Qaraldi: 27 January 2017. Hujayrasiz hayot]]
  5. ↑ Ma, Wentao (2016-09-26). "The essence of life". Biology Direct 11 (1): 49. doi:10.1186/s13062-016-0150-5. ISSN 1745-6150. PMID 27671203. PMC 5037589. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5037589. 
  6. ↑ Villarreal, Luis P. (December 2004). "Are Viruses Alive?". Scientific American 291 (6): 100–105. doi:10.1038/scientificamerican1204-100. PMID 15597986. http://www.scientificamerican.com/article.cfm?id=are-viruses-alive-2004. Qaraldi: 2013-04-27. Hujayrasiz hayot]]
  7. ↑ Forterre, Patrick (3 March 2010). "Defining Life: The Virus Viewpoint". Orig Life Evol Biosph 40 (2): 151–160. doi:10.1007/s11084-010-9194-1. PMID 20198436. PMC 2837877. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2837877. 
  8. ↑ Lwoff, A. (1957-01-01). "The Concept of Virus". Microbiology 17 (2): 239–253. doi:10.1099/00221287-17-2-239. PMID 13481308. 
  9. ↑ "Potato spindle tuber "virus". IV. A replicating, low molecular weight RNA". Virology 45 (2): 411–28. August 1971. doi:10.1016/0042-6822(71)90342-4. PMID 5095900. 
  10. ↑ „ARS Research Timeline – Tracking the Elusive Viroid“ (2006-yil 2-mart). 2007-yil 6-iyulda asl nusxadan arxivlangan. Qaraldi: 2007-yil 18-iyul.
  11. ↑ Tsagris, E. M.; Martínez De Alba, A. E.; Gozmanova, M; Kalantidis, K (2008). "Viroids". Cellular Microbiology 10 (11): 2168–79. doi:10.1111/j.1462-5822.2008.01231.x. PMID 18764915. 
  12. ↑ Daròs, J. A.; Elena, S. F.; Flores (2006). "Viroids: An Ariadne's thread into the RNA labyrinth". EMBO Reports 7 (6): 593–598. doi:10.1038/sj.embor.7400706. PMID 16741503. PMC 1479586. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1479586. 
  13. ↑ Diener, T. O. (1989). "Circular RNAs: Relics of precellular evolution?". Proceedings of the National Academy of Sciences of the United States of America 86 (23): 9370–4. doi:10.1073/pnas.86.23.9370. PMID 2480600. PMC 298497. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=298497. 
  14. ↑ Villarreal, Luis P.. Viruses and the evolution of life. Washington, D.C.: ASM Press, 2005 — 31-bet. ISBN 1-55581-309-7. 
  15. ↑ Flores, R; Gago-Zachert, S.; Serra, P.; Sanjuán, R.; Elena, S. F. (2014). "Viroids: Survivors from the RNA world?". Annual Review of Microbiology 68: 395–414. doi:10.1146/annurev-micro-091313-103416. PMID 25002087. https://digital.csic.es/bitstream/10261/107724/1/Annu.%20Rev.%20Microbiol.%20Flores%20et%20al%202014.pdf. Qaraldi: 15 December 2018. Hujayrasiz hayot]]
  16. ↑ Zimmer, Carl. „A Tiny Emissary From the Ancient Past“. The New York Times (2014-yil 25-sentyabr). 2014-yil 27-sentyabrda asl nusxadan arxivlangan. Qaraldi: 2014-yil 22-noyabr.
  17. ↑ Sidik, Saima (29 January 2024). "'Wildly weird' RNA bits discovered infesting the microbes in our guts". Nature. doi:10.1038/d41586-024-00266-7. PMID 38291328. https://www.nature.com/articles/d41586-024-00266-7. Qaraldi: 31 January 2024. Hujayrasiz hayot]]
  18. ↑ Pennisi, Elizabeth (26 January 2024). 'It's insane': New viruslike entities found in human gut microbes. doi:10.1126/science.znxt3dk. https://www.science.org/content/article/it-s-insane-new-viruslike-entities-found-human-gut-microbes. Qaraldi: 31 January 2024. Hujayrasiz hayot]]
  19. ↑ Prosdocimi, Francisco; José, Marco V.; de Farias, Sávio Torres (2019), Pontarotti, Pierre (muh.), „The First Universal Common Ancestor (FUCA) as the Earliest Ancestor of LUCA's (Last UCA) Lineage“, Evolution, Origin of Life, Concepts and Methods, Cham: Springer International Publishing, 43–54-bet, doi:10.1007/978-3-030-30363-1_3, ISBN 978-3-030-30363-1, S2CID 199534387, 8 March 2024da asl nusxadan arxivlandi, qaraldi: 2023-11-02 
"https://uz.wikipedia.org/w/index.php?title=Hujayrasiz_hayot&oldid=5880776" dan olindi