DNA和RNA有何不同,有甚么用,如何组成?
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想像DNA是一部电影的胶卷，RNA是放映的设备，而蛋白质便是一场声色俱佳的电影！您是否能由这个比喻中，体会到RNA在细胞内所扮演的角色？DNA与RNA的差异到底到哪儿？德国的细胞学家福尔根解开了这个谜题 DNA与RNA的结构差异： DNA是双链，RNA是单链 两者在五碳糖的第二个碳原子上，DNA连接的是氢原子，而RNA连接的是羟基 DNA所含的碱基种类为ATCG，而RNA为AU（尿嘧啶）CG 2006-10-24 17:16:51 补充： 希望这个令你更易明白！ mod.life.nthu.edu/protein/PTRC/Flash/TRANSCRIPTION.SWF
参考: biotech.nstm/02/025
遗传学是研究基因对个体表现的特征，甚么是叫基因呢(Gene)，基因是每个人从父母得下来的遗传基本单元，它决定每个个体表现的特征，基因十分细小，无法从肉眼可以看见却藏着生物化学DNA的讯息。排列在人体细胞内的46条染色体 (Chromosome)上-46条染色体可分为23对，包括22对常染色体或者管理身体各种特征的染色体和另外一对是性染色体，决定个人的性别。当基因运作上出现错误，便会导至三种遗传病例。 Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. RNA nucleotides contain ribose rings and uracil unlike deoxyribonucleic acid (DNA)
which contains deoxyribose and thymine. It is trcribed from DNA by enzymes called RNA polymerases and further processed by other enzymes. RNA serves as the template for trlation of genes into proteins
trferring amino acids to the ribosome to form proteins
and also trlating the trcript into proteins. Nucleic acids were discovered in 1869 by Johann Friedrich Miescher (1844-1895)
who called the material 'nuclein' since it was found in the nucleus. It was later discovered that prokaryotic cells
which do not have a nucleus
also contain nucleic acids. The role of RNA in protein synthesis had been suspected since 1939
based on experiments carried out by Torbjörn Cersson
Jean Brachet and Jack Schultz. The sequence of the 77 nucleotides of a yeast RNA was found by Robert W. Holley in 1964
winning Holley the 1968 Nobel Prize for Medicine. RNA is primarily made up of four different bases: adenine
guanine
cytosine
and uracil. The first three are the same as those found in DNA
but in DNA thymine replaces uracil as the base plementary to adenine. This base is also a pyrimidine and is very similar to thymine. Uracil is energetically less expensive to produce than thymine
which may account for its use in RNA. In DNA
however
uracil is readily produced by chemical degradation of cytosine
so having thymine as the normal base makes detection and repair of such incipient mutations more efficient. Thus
uracil is appropriate for RNA
where quantity is important but lifespan is not
whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical. There are also numerous modified bases found in RNA that serve many different roles. Pseudouridine (Ψ) and the DNA nucleoside thymidine are found in various places (most notably in the TΨC loop of every tRNA). There are nearly 100 other naturally occurring modified bases
many of which are not fully understood. [edit] Comparison with DNA Unlike DNA
RNA is almost always a single-stranded molecule and has a much shorter chain of nucleotides. RNA contains ribose
rather than the deoxyribose found in DNA (there is a hydroxyl group attached to the pentose ring in the 2' position whereas RNA has o hydroxyl groups). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Several types of RNA (tRNA
rRNA) contain a great deal of secondary structure
which help promote stability. Like DNA
most biologically active RNAs including tRNA
rRNA
snRNAs and other non-coding RNAs (such as the SRP RNAs) are extensively base paired to form double stranded helices. Structural *** ysis of these RNAs have revealed that they are not
"single-stranded" but rather highly structured. Unlike DNA
this structure is not just limited to long double-stranded helices but rather collections of short helices packed together into structures akin to proteins. In this fashion
RNAs can achieve chemical catalysis
like enzymes. For instance
determination of the structure of the ribosome in 2000 revealed that the active site of this enzyme that catalyzes peptide bond formation is posed entirely of RNA.
参考: biotech.nstm/02/025
遗传学是研究基因对个体表现的特征，甚么是叫基因呢(Gene)，基因是每个人从父母得下来的遗传基本单元，它决定每个个体表现的特征，基因十分细小，无法从肉眼可以看见却藏着生物化学DNA的讯息。排列在人体细胞内的46条染色体 (Chromosome)上-46条染色体可分为23对，包括22对常染色体或者管理身体各种特征的染色体和另外一对是性染色体，决定个人的性别。当基因运作上出现错误，便会导至三种遗传病例。 Ribonucleic acid (RNA) is a nucleic acid polymer consisting of nucleotide monomers. RNA nucleotides contain ribose rings and uracil unlike deoxyribonucleic acid (DNA)
which contains deoxyribose and thymine. It is trcribed from DNA by enzymes called RNA polymerases and further processed by other enzymes. RNA serves as the template for trlation of genes into proteins
trferring amino acids to the ribosome to form proteins
and also trlating the trcript into proteins. Nucleic acids were discovered in 1869 by Johann Friedrich Miescher (1844-1895)
who called the material 'nuclein' since it was found in the nucleus. It was later discovered that prokaryotic cells
which do not have a nucleus
also contain nucleic acids. The role of RNA in protein synthesis had been suspected since 1939
based on experiments carried out by Torbjörn Cersson
Jean Brachet and Jack Schultz. The sequence of the 77 nucleotides of a yeast RNA was found by Robert W. Holley in 1964
winning Holley the 1968 Nobel Prize for Medicine. RNA is primarily made up of four different bases: adenine
guanine
cytosine
and uracil. The first three are the same as those found in DNA
but in DNA thymine replaces uracil as the base plementary to adenine. This base is also a pyrimidine and is very similar to thymine. Uracil is energetically less expensive to produce than thymine
which may account for its use in RNA. In DNA
however
uracil is readily produced by chemical degradation of cytosine
so having thymine as the normal base makes detection and repair of such incipient mutations more efficient. Thus
uracil is appropriate for RNA
where quantity is important but lifespan is not
whereas thymine is appropriate for DNA where maintaining sequence with high fidelity is more critical. There are also numerous modified bases found in RNA that serve many different roles. Pseudouridine (Ψ) and the DNA nucleoside thymidine are found in various places (most notably in the TΨC loop of every tRNA). There are nearly 100 other naturally occurring modified bases
many of which are not fully understood. [edit] Comparison with DNA Unlike DNA
RNA is almost always a single-stranded molecule and has a much shorter chain of nucleotides. RNA contains ribose
rather than the deoxyribose found in DNA (there is a hydroxyl group attached to the pentose ring in the 2' position whereas RNA has o hydroxyl groups). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Several types of RNA (tRNA
rRNA) contain a great deal of secondary structure
which help promote stability. Like DNA
most biologically active RNAs including tRNA
rRNA
snRNAs and other non-coding RNAs (such as the SRP RNAs) are extensively base paired to form double stranded helices. Structural *** ysis of these RNAs have revealed that they are not
"single-stranded" but rather highly structured. Unlike DNA
this structure is not just limited to long double-stranded helices but rather collections of short helices packed together into structures akin to proteins. In this fashion
RNAs can achieve chemical catalysis
like enzymes. For instance
determination of the structure of the ribosome in 2000 revealed that the active site of this enzyme that catalyzes peptide bond formation is posed entirely of RNA.
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