Relationship between DNA, RNA and proteins

Even though we stated at the beginning of this section that it is not our purpose to discuss the biological function of the macromolecules described, it is hard to resist saying a few words about some of their most important interactions. First, it is easy to visualize how the structure of DNA leads to its replication and hence the transfer of genetic information which is coded in the sequence of bases along the chain. Specifically, when the DNA double helix opens up it exposes the sequence of bases in each strand of the molecule. In a solution where bases, sugars and phosphates are available or can be synthesized, it is possible to form the complementary strand of each of the two strands of the parent molecule. This results in 

The first part of this process is referred to as transcription, and the second part is referred to as translation. While the process by which the whole task is 

A three-base group that corresponds to a specific aminoacid is called a codon. The correspondence between the 64 codons and the 20 aminoacids is given in Table 13.4. Notice that certain codons, specifically t/A A, t/GA, /AG, do notform aminoacids but correspond to the STOP signal when these codons are encountered, the aminoacid sequence is terminated and the protein is complete. Only one codon corresponds to the aminoacid Met, namely AGG this codon signifies the start of the protein when it is at the beginning of the sequence, as well as the aminoacid Met when it is in the middle. The following is an example of a DNA section that has been transcribed into an mRNA section, which is then translated into an aminoacid sequence which forms part of a protein  

This is not a random sequence but turns out to be part of the RNA of the AIDS virus. Thus, although the process of protein formation involves three types of RNA molecules and a remarkably complex molecular factory of proteins, the ribosome, the transcription code is beautifully simple. This genetic code, including the bases, aminoacids and codons, is essentially universal for all living organisms  

We need to clarify one important point in the transcription of genetic information discussed above. This has to do with the precise sequence of bases in DNA that is transcribed into mRNA and then translated into a protein or group of proteins. Organisms are classified into two broad categories, those whose cells contain a nucleus, called eucaryotes, and those whose cells do not have a nucleus, called 

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