‘Several questions about origin of life have been answered, but much remains to be studied’’ said Stanley Miller and Harold Urey way back in 1959 after reporting laboratory synthesis of amino acids in primitive earth conditions. Many advances down the line yet the scientists have long been grappling with a fundamental question – which genetic material was first to be formed on the primitive earth, 的DNA or RNA, or a bit of both? There is evidence now to suggest that 的DNA 和 RNA both may have co-existed in the primordial soup from where the life forms may have evolved with respective genetic materials.
分子生物学的中心法则指出 的DNA & RNA & 蛋白质. 蛋白质 are responsible for majority, if not all the reactions taking place in an organism. The entire functionality of an organism is majorly dependent upon their presence and interaction of 蛋白质 molecules. According to central dogma, 蛋白质 are produced by the information contained in 的DNA which is converted to functional 蛋白质 via a messenger called RNA. However, it is possible that 蛋白质 themselves can survive independently without any 的DNA or RNA, as is the case with prions (misfolded 蛋白质 molecules that do not contain 的DNA or RNA), but can survive on their own.
因此，生命起源可以分为三种情况。
A) If the 蛋白质 or its building blocks were able to form abiotically during the atmosphere that existed billions of years ago in primordial soup, 蛋白质 can be termed as the basis of 生命的起源. 支持它的实验证据来自斯坦利米勒的著名实验1，2，这表明当甲烷、氨、水和氢气的混合物混合在一起并循环通过放电时，会形成氨基酸的混合物。 七年后再次证实了这一点3 Stanley Miller 和 Harold Urey 于 1959 年指出，原始地球中还原性大气的存在导致了 有机 在上述气体加上少量一氧化碳和二氧化碳存在下的化合物。米勒-尤里实验的相关性多年来一直受到科学界的质疑，他们认为他们研究中使用的气体混合物相对于原始地球上存在的条件来说过于还原。许多理论指出中性大气含有过量的二氧化碳、氮气和水蒸气4. 然而，中性气氛也被认为是合成氨基酸的合理环境5. 此外，对于 蛋白质 to act as origins of life, they need to self-replicating leading to a combination of different 蛋白质 to cater to different reactions taking place in an organism.
B) 如果原始汤提供了积木的条件 的DNA 和 RNA to be formed, then either of these could have been the genetic material. The research until now favoured RNA to be the genetic material for the origin of life forms due to their capability of folding upon itself, existing as a single strand and acting as an enzyme6, capable of making more RNA molecules. A number of self-replicating RNA enzymes7 have been discovered over the years suggesting RNA to be the starting genetic material. This was further strengthened by the research performed by John Sutherland’s group that led to the formation of two bases of RNA in an environment similar to primordial soup by including phosphate in the mixture8. 通过模拟还原气氛（包含氨、一氧化碳和水），类似于米勒-尤里实验中使用的气氛，然后通过放电和高功率激光通过它们，也可以形成 RNA 构建块9. If RNA is to be believed to be the originator, then when and how did 的DNA and proteins come into being? Did 的DNA develop as a genetic material later because of the unstable nature of RNA and proteins followed suit. Answers to all these questions still remain unanswered.
C) DNA 和 RNA 可以在导致生命起源的原始汤中共存的第三种情况来自于 3 月发表的研究rd June 2020 by John Sutherland’s group from the MRC Laboratory at Cambridge, UK. The researchers simulated the conditions that existed on a primordial Earth billions of years ago, with shallow ponds in the lab. They first dissolved chemicals that form RNA in water, followed by drying and heating them and then subjecting them to UV radiation that simulated sun’s rays existing in primordial time. This not only led to the synthesis of the two building blocks of RNA 而且 的DNA, suggesting that both nucleic acids co-existed at the time of origin of life10.
根据当今存在的当代知识并尊重分子生物学的中心法则，DNA 和 RNA 共存导致生命起源和蛋白质形成的出现似乎是有道理的。
然而，作者希望推测另一种情况，其中所有三个重要的生物大分子，即。 DNA、RNA和蛋白质一起存在于原始汤中。 原始汤中存在的混乱条件，包括地球表面的化学性质、火山爆发以及氨、甲烷、一氧化碳、二氧化碳和水等气体的存在，可能是所有大分子形成的理想条件。 Ferus 等人的研究表明了这一点，其中核碱基是在相同的还原气氛中形成的9 用于米勒-尤里的实验。 如果我们相信这个假设，那么在进化过程中，不同的生物体采用了一种或另一种遗传物质，这有利于它们的生存向前发展。
然而，当我们试图了解生命形式的起源时，还需要更多的研究来回答关于生命如何起源和传播的基本和相关问题。 这将需要一种“开箱即用”的方法，而不依赖于当前科学所遵循的教条在我们的思维中引入的任何偏见。
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