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*[[催化]]简单化学反应的能力——即RNA分子能通过折叠形成催化中心。<!--
*[[催化]]简单化学反应的能力——即RNA分子能通过折叠形成催化中心。<!--
这句什么意思？
这句什么意思？
(i.e., a strand of RNA which would make creating more strands of RNA easier).-->在实验室中，一些相对较短的RNA分子已具有该能力<ref>Huang, Yang, and Yarus, [http://www.chembiol.com/content/article/abstract?uid=PIIS1074552198902940 RNA enzymes with two small-molecule substrates] {{Webarchive|url=https://archive.is/20120703153110/http://www.chembiol.com/content/article/abstract?uid=PIIS1074552198902940 |date=2012-07-03 }}. Chemistry & Biology, Vol 5, 669-678, November 1998</ref><ref>{{cite journal |last=Unrau |first=P. J. |authorlink= |author2=Bartel, D. P. |year=1998 |title=RNA-catalysed nucleotide synthesis |journal=Nature |volume=395 |issue=6699 |pages=260–263 |doi=10.1038/26193 |url=|pmid=9751052 |bibcode = 1998Natur.395..260U }}</ref>。
(i.e., a strand of RNA which would make creating more strands of RNA easier).-->在实验室中，一些相对较短的RNA分子已具有该能力<ref>Huang, Yang, and Yarus, [http://www.chembiol.com/content/article/abstract?uid=PIIS1074552198902940 RNA enzymes with two small-molecule substrates] {{Webarchive|url=https://archive.today/20120703153110/http://www.chembiol.com/content/article/abstract?uid=PIIS1074552198902940 |date=2012-07-03 }}. Chemistry & Biology, Vol 5, 669-678, November 1998</ref><ref>{{cite journal |last=Unrau |first=P. J. |authorlink= |author2=Bartel, D. P. |year=1998 |title=RNA-catalysed nucleotide synthesis |journal=Nature |volume=395 |issue=6699 |pages=260–263 |doi=10.1038/26193 |url=|pmid=9751052 |bibcode = 1998Natur.395..260U }}</ref>。
*在RNA的3'-端结合[[氨基酸]]的能力，以使用其侧链基团的化学性质<ref name="pmid21779963">{{cite journal | author = Erives A | title = A Model of Proto-Anti-Codon RNA Enzymes Requiring L-Amino Acid Homochirality | journal = J Molecular Evolution | volume = 73 | pages= 10–22 | year = 2011 | pmid = 21779963 | doi = 10.1007/s00239-011-9453-4 | pmc=3223571 | issue = 1–2}}</ref>。
*在RNA的3'-端结合[[氨基酸]]的能力，以使用其侧链基团的化学性质<ref name="pmid21779963">{{cite journal | author = Erives A | title = A Model of Proto-Anti-Codon RNA Enzymes Requiring L-Amino Acid Homochirality | journal = J Molecular Evolution | volume = 73 | pages= 10–22 | year = 2011 | pmid = 21779963 | doi = 10.1007/s00239-011-9453-4 | pmc=3223571 | issue = 1–2}}</ref>。
*催化[[肽键]]形成的能力，以生成短[[肽]]乃至更长的[[蛋白质]]。这一任务在现代的细胞中由[[核糖体]]完成。核糖体是由几个RNA（称为[[rRNA]]）和一些蛋白质（称为[[核糖体蛋白质]]）组成的复合体，其中rRNA负责催化，核糖体蛋白质上的氨基酸残基都距离[[活性位点]]的18[[埃|Å]]以上<ref name="Atk06" />。在实验室中合成了更短的能催化[[肽键]]生成的RNA，这暗示着rRNA可能由更短的RNA进化而来<ref>{{cite journal |last=Zhang |first=Biliang |authorlink= |author2=Cech, Thomas R. |year=1997 |title=Peptide bond formation by ''in vitro'' selected ribozymes |journal=Nature |volume=390 |issue=6655 |pages=96–100 |doi=10.1038/36375 |url=|pmid=9363898 |bibcode = 1997Natur.390...96Z }}</ref>。它也表明，氨基酸在进化出复杂的肽链之前，是以[[辅因子]]的形式参与RNA的反应，以提高其活性或使反应更多样化。类似地，[[tRNA]]在作为转运氨基酸的载体之前可能另有他用<ref>{{cite journal |last=Szathmary |first=E. |authorlink= |year=1999 |title=The origin of the genetic code: amino acids as cofactors in an RNA world |journal=Trends in Genetics |volume=15 |issue=6 |pages=223–229 |doi=10.1016/S0168-9525(99)01730-8 |url=|pmid=10354582 }}</ref>。
*催化[[肽键]]形成的能力，以生成短[[肽]]乃至更长的[[蛋白质]]。这一任务在现代的细胞中由[[核糖体]]完成。核糖体是由几个RNA（称为[[rRNA]]）和一些蛋白质（称为[[核糖体蛋白质]]）组成的复合体，其中rRNA负责催化，核糖体蛋白质上的氨基酸残基都距离[[活性位点]]的18[[埃|Å]]以上<ref name="Atk06" />。在实验室中合成了更短的能催化[[肽键]]生成的RNA，这暗示着rRNA可能由更短的RNA进化而来<ref>{{cite journal |last=Zhang |first=Biliang |authorlink= |author2=Cech, Thomas R. |year=1997 |title=Peptide bond formation by ''in vitro'' selected ribozymes |journal=Nature |volume=390 |issue=6655 |pages=96–100 |doi=10.1038/36375 |url=|pmid=9363898 |bibcode = 1997Natur.390...96Z }}</ref>。它也表明，氨基酸在进化出复杂的肽链之前，是以[[辅因子]]的形式参与RNA的反应，以提高其活性或使反应更多样化。类似地，[[tRNA]]在作为转运氨基酸的载体之前可能另有他用<ref>{{cite journal |last=Szathmary |first=E. |authorlink= |year=1999 |title=The origin of the genetic code: amino acids as cofactors in an RNA world |journal=Trends in Genetics |volume=15 |issue=6 |pages=223–229 |doi=10.1016/S0168-9525(99)01730-8 |url=|pmid=10354582 }}</ref>。
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====RNA信息存储的局限性====
====RNA信息存储的局限性====
RNA的化学性质使得大RNA分子本身比较脆弱。他们可以很容易地水解成构成自身的核苷酸。<ref>{{cite journal|title=Instability and decay of the primary structure of DNA|first=T|last=Lindahl|date=April 1993|journal=Nature|volume=362|issue=6422|pages=709–15|pmid=8469282|doi=10.1038/362709a0|bibcode = 1993Natur.362..709L }}</ref><ref>{{cite journal|title=Ancient DNA|journal=Scientific American|first=S|last=Pääbo|volume=269|pages=60–66|date=November 1993|issue=5|doi=10.1038/scientificamerican1193-86}}</ref> 这些局限并没有使RNA不能储存信息，不过由于一些能量需要用来修补和替换损坏的RNA分子，这种储存方式会更加耗费能量。而且变异的可能性也会增加。虽然这些特性使得RNA不适合用于今天的“DNA优化”的生命体，但是对于更加原始的生命体来说，这些也许是可以接受的。
RNA的化学性质使得大RNA分子本身比较脆弱。他们可以很容易地水解成构成自身的核苷酸。<ref>{{cite journal|title=Instability and decay of the primary structure of DNA|first=T|last=Lindahl|date=April 1993|journal=Nature|volume=362|issue=6422|pages=709–15|pmid=8469282|doi=10.1038/362709a0|bibcode = 1993Natur.362..709L }}</ref><ref>{{cite journal|title=Ancient DNA|url=https://archive.org/details/sim_scientific-american_1993-11_269_5/page/60|journal=Scientific American|first=S|last=Pääbo|volume=269|pages=60–66|date=November 1993|issue=5|doi=10.1038/scientificamerican1193-86}}</ref> 这些局限并没有使RNA不能储存信息，不过由于一些能量需要用来修补和替换损坏的RNA分子，这种储存方式会更加耗费能量。而且变异的可能性也会增加。虽然这些特性使得RNA不适合用于今天的“DNA优化”的生命体，但是对于更加原始的生命体来说，这些也许是可以接受的。
===RNA作为调控物质===
===RNA作为调控物质===
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RNA世界假说能被诸如RNA能像[[DNA]]一样存储、传递、复制[[遗传学|遗传]]信息；RNA能作为[[核酶]]进行催化等证据支持，因它能执行DNA和蛋白质的任务，故被认为是生命起源的物质形式<ref name="Atk06" />。一些[[病毒]]也使用RNA而不是DNA作为其遗传信息载体<ref>Patton, John T. Editor (2008). Segmented Double-stranded RNA Viruses: Structure and Molecular Biology. Caister Academic Press. Editor's affiliation: Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, MD 20892-8026. ISBN 978-1-904455-21-9</ref>。虽然[[核苷酸]]并未在[[米勒-尤里实验|米勒-尤里]]关于[[生命起源]]的实验中出现，但它们可能的[[前体]]已有报道<ref name=Powner />，[[嘌呤]]碱基如[[腺嘌呤]]可能由[[氰化氢]]{{le|五聚体|pentamer|五聚化}}生成。对{{le|Qβ噬菌体|Bacteriophage Qβ}}RNA的实验也展示了RNA的自我复制能力<!-- I don't want to link to Spiegelman Monster here because I'm not sure that this is what's being talked about, but it appears to be. --><ref>Bell, Graham: The Basics of Selection. Springer, 1997.</ref>由于目前没有已知的化学途径能够在生命起源以前的条件下以[[胞嘧啶]]和[[尿嘧啶]]为原料非生源合成[[核苷酸]]，有些人认为当时出现的核酸并不包括这些能够在如今的生命中发现的碱基<ref>{{cite journal |last=Orgel |first=L. |authorlink= |year=1994 |title=The origin of life on earth |url=https://archive.org/details/sim_scientific-american_1994-10_271_4/page/81 |journal=Scientific American |volume=271 |issue=4 |pages=81 |doi=10.1038/scientificamerican1094-76 |pmid=7524147}}</ref>。胞嘧啶核糖核苷在100 °C（212 °F）下半衰期为19天，在冰水中半衰期为17000年，有些人认为对于核酸的积累来说这在[[地质年代]]上太短<ref>{{cite journal |last=Levy |first=Matthew |authorlink= |author2=Miller, Stanley L. |year=1998 |title=The stability of the RNA bases: Implications for the origin of life |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=95 |issue=14 |pages=7933–7938 |doi=10.1073/pnas.95.14.7933|pmid=9653118 |pmc=20907|bibcode = 1998PNAS...95.7933L }}</ref>。其他人怀疑[[核糖]]和其他糖链骨架能否在找到原始基因的原料的过程中保持稳定，<ref>{{cite journal |last=Larralde |first=R. |authorlink= |author2=Robertson, M. P. |author3=Miller, S. L. |year=1995 |title=Rates of decomposition of ribose and other sugars: implications for chemical evolution |journal=PNAS |volume=92 |issue=18 |pages=8158–8160|doi=10.1073/pnas.92.18.8158 |pmid=7667262 |pmc=41115 |bibcode = 1995PNAS...92.8158L }}</ref>他们也提出所有的核糖分子必须为一样的[[对映异构体]]，因为[[手性]]不一样的核苷酸会成为一个核苷酸链的[[终止子]]<ref>{{cite journal |title=Chiral selection in poly(C)-directed synthesis of oligo(G) |author=Joyce GF |author2=et al. |journal=Nature |pmid=6462250 |year=1984 |issue=5978 |volume=310 |pages=602–604 |doi=10.1038/310602a0|bibcode = 1984Natur.310..602J }}</ref>。
RNA世界假说能被诸如RNA能像[[DNA]]一样存储、传递、复制[[遗传学|遗传]]信息；RNA能作为[[核酶]]进行催化等证据支持，因它能执行DNA和蛋白质的任务，故被认为是生命起源的物质形式<ref name="Atk06" />。一些[[病毒]]也使用RNA而不是DNA作为其遗传信息载体<ref>Patton, John T. Editor (2008). Segmented Double-stranded RNA Viruses: Structure and Molecular Biology. Caister Academic Press. Editor's affiliation: Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, MD 20892-8026. ISBN 978-1-904455-21-9</ref>。虽然[[核苷酸]]并未在[[米勒-尤里实验|米勒-尤里]]关于[[生命起源]]的实验中出现，但它们可能的[[前体]]已有报道<ref name=Powner />，[[嘌呤]]碱基如[[腺嘌呤]]可能由[[氰化氢]]{{le|五聚体|pentamer|五聚化}}生成。对{{le|Qβ噬菌体|Bacteriophage Qβ}}RNA的实验也展示了RNA的自我复制能力<!-- I don't want to link to Spiegelman Monster here because I'm not sure that this is what's being talked about, but it appears to be. --><ref>Bell, Graham: The Basics of Selection. Springer, 1997.</ref>由于目前没有已知的化学途径能够在生命起源以前的条件下以[[胞嘧啶]]和[[尿嘧啶]]为原料非生源合成[[核苷酸]]，有些人认为当时出现的核酸并不包括这些能够在如今的生命中发现的碱基<ref>{{cite journal |last=Orgel |first=L. |authorlink= |year=1994 |title=The origin of life on earth |url=https://archive.org/details/sim_scientific-american_1994-10_271_4/page/81 |journal=Scientific American |volume=271 |issue=4 |pages=81 |doi=10.1038/scientificamerican1094-76 |pmid=7524147}}</ref>。胞嘧啶核糖核苷在100 °C（212 °F）下半衰期为19天，在冰水中半衰期为17000年，有些人认为对于核酸的积累来说这在[[地质年代]]上太短<ref>{{cite journal |last=Levy |first=Matthew |authorlink= |author2=Miller, Stanley L. |year=1998 |title=The stability of the RNA bases: Implications for the origin of life |journal=[[Proceedings of the National Academy of Sciences|PNAS]] |volume=95 |issue=14 |pages=7933–7938 |doi=10.1073/pnas.95.14.7933|pmid=9653118 |pmc=20907|bibcode = 1998PNAS...95.7933L }}</ref>。其他人怀疑[[核糖]]和其他糖链骨架能否在找到原始基因的原料的过程中保持稳定，<ref>{{cite journal |last=Larralde |first=R. |authorlink= |author2=Robertson, M. P. |author3=Miller, S. L. |year=1995 |title=Rates of decomposition of ribose and other sugars: implications for chemical evolution |journal=PNAS |volume=92 |issue=18 |pages=8158–8160|doi=10.1073/pnas.92.18.8158 |pmid=7667262 |pmc=41115 |bibcode = 1995PNAS...92.8158L }}</ref>他们也提出所有的核糖分子必须为一样的[[对映异构体]]，因为[[手性]]不一样的核苷酸会成为一个核苷酸链的[[终止子]]<ref>{{cite journal |title=Chiral selection in poly(C)-directed synthesis of oligo(G) |author=Joyce GF |author2=et al. |journal=Nature |pmid=6462250 |year=1984 |issue=5978 |volume=310 |pages=602–604 |doi=10.1038/310602a0|bibcode = 1984Natur.310..602J }}</ref>。
===“分子生物学之梦”===
===“分子生物学之梦”===
“分子生物学之梦”（{{lang|en|"Molecular biologist's dream"}}）这个提法由生化学家[[傑拉德·喬伊斯]]和{{tsl|en|Leslie Orgel|莱斯利·奥格尔}}提出，指在实验室得到第一个能[[自我复制]]的[[RNA]]分子，正如其它与RNA世界相关的实验，它的成功取决于对前生命{{le|早期地球|early Earth}}的精确模拟，但在这一点上常常失之千里<ref name="arn">{{cite web|url=http://www.arn.org/docs/odesign/od171/rnaworld171.htm|title=The RNA World: A Critique|publisher=[[Access Research Network]]|author=Gordon C. Mills, Dean Kenyon|accessdate=2011-09-10|archive-date=2011-08-30|archive-url=https://web.archive.org/web/20110830115637/http://www.arn.org/docs/odesign/od171/rnaworld171.htm|dead-url=no}}</ref>。值得注意的是，目前已知的[[核苷酸]]合成步骤中有许多都难以在前生命条件下进行<ref>{{cite book | last = Schopf| first = J. William| title = Life's origin: the beginnings of biological evolution| url = https://archive.org/details/lifesoriginbegin00scho| publisher =University of California Press|year =2002| page = [https://archive.org/details/lifesoriginbegin00scho/page/n156 150]| isbn =0-520-23390-5}}</ref>。喬伊斯和奥格尔特别指出分子生物学之梦需要“魔法般的[[催化]]”来将核苷酸转化为随机序列的多聚核苷酸，并使其有复制活性<ref name="arn"/>。
“分子生物学之梦”（{{lang|en|"Molecular biologist's dream"}}）这个提法由生化学家[[傑拉德·喬伊斯]]和[[莱斯利·奥格尔]]提出，指在实验室得到第一个能[[自我复制]]的[[RNA]]分子，正如其它与RNA世界相关的实验，它的成功取决于对前生命{{le|早期地球|early Earth}}的精确模拟，但在这一点上常常失之千里<ref name="arn">{{cite web|url=http://www.arn.org/docs/odesign/od171/rnaworld171.htm|title=The RNA World: A Critique|publisher=[[Access Research Network]]|author=Gordon C. Mills, Dean Kenyon|accessdate=2011-09-10|archive-date=2011-08-30|archive-url=https://web.archive.org/web/20110830115637/http://www.arn.org/docs/odesign/od171/rnaworld171.htm|dead-url=no}}</ref>。值得注意的是，目前已知的[[核苷酸]]合成步骤中有许多都难以在前生命条件下进行<ref>{{cite book | last = Schopf| first = J. William| title = Life's origin: the beginnings of biological evolution| url = https://archive.org/details/lifesoriginbegin00scho| publisher =University of California Press|year =2002| page = [https://archive.org/details/lifesoriginbegin00scho/page/n156 150]| isbn =0-520-23390-5}}</ref>。喬伊斯和奥格尔特别指出分子生物学之梦需要“魔法般的[[催化]]”来将核苷酸转化为随机序列的多聚核苷酸，并使其有复制活性<ref name="arn"/>。
^ 4.04.14.24.3Cech, T.R. (2011). The RNA Worlds in Context. Source: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215. Cold Spring Harb Perspect Biol. 2011 Feb 16. pii: cshperspect.a006742v1. doi:10.1101/cshperspect.a006742. [Epub ahead of print]
^Woese C.R. (1967). The genetic code: The molecular basis for genetic expression. p. 186. Harper & Row
^ 11.011.111.211.311.4Atkins, John F.; Gesteland, Raymond F.; Cech, Thomas. The RNA world: the nature of modern RNA suggests a prebiotic RNA world. Plainview, N.Y: Cold Spring Harbor Laboratory Press. 2006. ISBN 0-87969-739-3.
^Sutherland, J.D; Anastasi, C., Buchet F.F, Crower M.A, Parkes A.L, Powner M. W., Smith J.M. RNA: Prebiotic Product, or Biotic Invention. Chemistry & Biodiversity. April 2007, 4 (4): 721–739. PMID 17443885. doi:10.1002/cbdv.200790060.引文使用过时参数coauthors (帮助)
^Forster AC, Symons RH. Self-cleavage of plus and minus RNAs of a virusoid and a structural model for the active sites. Cell. 1987, 49 (2): 211–220. PMID 2436805. doi:10.1016/0092-8674(87)90562-9.
^Tucker BJ, Breaker RR. Riboswitches as versatile gene control elements. Current Opinion in Structural Biology. 2005, 15 (3): 342–8. PMID 15919195. doi:10.1016/j.sbi.2005.05.003.
^Switching the light on plant riboswitches. Samuel Bocobza and Asaph Aharoni Trends in Plant Science Volume 13, Issue 10, October 2008, Pages 526-533 doi:10.1016/j.tplants.2008.07.004PMID 18778966
. PMID 20739415. doi:10.1101/cshperspect.a003608. "There is now strong evidence indicating that an RNA World did indeed exist before DNA- and protein-based life."