What is the Central Dogma of Molecular Biology

The central dogma of molecular biology describes the flow of information from DNA through RNA into proteins. This flow of information is called gene expression. It occurs through two main processes: transcription and translation. Transcription is the synthesis of an RNA molecule that contains the coding sequence of a gene. Translation follows transcription and in which the amino acid sequence of a gene is synthesized based on the coding sequence in mRNA.

Key Areas Covered

1. What is the Central Dogma of Molecular Biology
       –  The flow of Information in DNA
2. What are the Unusual Flows of Information
       – Reverse Transcription, RNA Replication, Direct Translation

Key Terms: Central Dogma of Molecular Biology, DNA, Proteins, RNA, Transcription, Translation

What is the Central Dogma of Molecular Biology

The central dogma of molecular biology describes the process by which the information in genes flows into proteins: DNA → RNA → protein. DNA contains genes that code for proteins. RNA is the intermediate between DNA and proteins. It carries information in genes from the nucleus to the cytoplasm in eukaryotes. Proteins are the determinants of the structure and the function of a particular cell. A protein is composed of an amino acid sequence, which is the coding sequence of a gene. Gene expression is the process of synthesizing proteins based on the instructions in genes. The two steps of gene expression are transcription and translation.

Figure 1: Central Dogma of Molecular Biology

What are Unusual Flows of Information

In addition to the universal flow of information from DNA to RNA to proteins, some alternative mechanisms occur in different types of organisms. Reverse transcription, RNA replication, and Direct translation of DNA into proteins are three such unusual flows of information.

Reverse Transcription

Transferring the information of RNA into DNA occurs during the reverse transcription process. It mainly occurs in retroviruses such as HIV. Also, reverse transcription occurs in retrotransposons and during telomere synthesis in eukaryotes. After reverse transcription, the information flow as usual from cDNA to RNA to Proteins.

RNA Replication

Copying of the RNA information into another RNA happens during the RNA replication process. The enzyme involved in RNA replication is RNA-dependent RNA polymerase. It occurs during RNA silencing and RNA editing in eukaryotes.

Direct Translation

Eukaryotic ribosomes can synthesize proteins from single-stranded DNA in vitro. Figure 2 shows the three types of unusual flow of information in green arrows.

Figure 2: Unusual Flow of Information

Conclusion

The central dogma of molecular biology describes the flow of information from DNA to RNA to proteins. Proteins synthesis is the mechanism of gene expression. It occurs through the transcription of DNA into RNA and translation of RNA into proteins.

Reference:

1. “4.1 Central Dogma of Molecular Biology.” CK-12 Foundation, Available here.

Image Courtesy:

1. “Central Dogma of Molecular Biochemistry with Enzymes” By Dhorspool at en.wikipedia (CC BY-SA 3.0) via Commons Wikimedia
2. “Extended Central Dogma with Enzymes” By User:Dhorspool (CC BY-SA 3.0) via Commons Wikimedia