genetic code

Article

January 27, 2022

The genetic code (遺傳符號), or genetic code (遺傳暗號), is a rule that determines which amino acid each codon encodes for. Encryption is meaningful in this context because they are paired so that they must match complementary, but there is also an expression of genetic code in addition to translation of genetic code. The meaning of the genetic code may be better explained in a coding system such as Morse code, ASCII code, and Unicode than a cryptosystem such as AES or RSA. Each code belonging to the genetic code is called a codon.

codon

A codon is the genetic information of messenger RNA and carrier RNA that designates one amino acid in gene expression.

History

Efforts to understand how proteins are encoded began after the discovery of the structure of DNA in 1953. The American astrophysicist George Gamow claimed that the 20 standard amino acids consisted of three bases. According to this argument, there are a total of four bases, and since a standard amino acid consists of three bases, a total of 64 sequences can exist. This argument was developed by Francis Crick and Sydney Brenner in 1961. Brenner), Leslie Barnett and RJ It was empirically proven by the joint experiment of R.J. Watts-Tobin. In the same year, the structure of the codon was studied and the structure was revealed by the experiments of Marshall Warren Nirenberg and Heinrich Matthaei.

Transcription and Codon Formation

In gene expression, the formation of a new protein begins with the formation of messenger RNA transcribed from DNA. When a specific nucleotide sequence constituting the DNA chain directs transcription and transcription is not required, a repressor enzyme is attached to prevent transcription. When a signal is received that the production of a specific protein is required, the repressor is detached from the DNA chain and transcription is initiated by RNA polymerase. RNA polymerase selects the direction of transcription and the DNA chain to be transcribed by the nucleotide sequence of the promoter at the transcription start point, binds to the operator, unwinds the DNA chain, and then starts transcription. RNA polymerase makes messenger RNA using ribonucleotides complementary to the DNA strand as a template. The base sequence of the messenger RNA made in this way is paired by three to form a codon. On the other hand, when RNA polymerase encounters a DNA sequence that indicates transcription termination, it stops transcription and is separated from the DNA.

Anticodone

Anticodon is a nucleotide sequence of a specific section constituting the RNA chain of the carrier RNA. The messenger RNA codon is translated by the ribosome and complementarily binds to the anticodon of the transport RNA carrying the amino acid. However, there are 45 anticodons that are complementary to each other, not 64.

Formation of protein

In the transport RNA, a portion of the RNA chain acts as an anticodon and the corresponding amino acid is attached to the end of the chain. The charged carrier RNA enters the ribosome and binds to the messenger RNA codon, and the ribosome removes amino acids from the end of the carrier RNA to form a polypeptide bond. The transport RNA, from which the amino acid has been broken off, comes out of the ribosome and transfers the amino acid back to the ribosome. On the other hand, the polypeptide made from the ribosome is folded into an appropriate three-dimensional structure to become a protein.

Amino Acids

20 kinds (phenylalanine, serine, tyrosine,

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