The exception to the Central Dogma

Author: William Tsay

Editor: Liane Xu

Artist: Jenny Li

A dogma is a principle that is unquestioningly true. In molecular biology, the central dogma refers to the flow of genetic information in which DNA makes protein. It suggests that DNA contains all information needed to make proteins, and that RNA is used as a messenger to carry the information to the ribosomes.

The first step to the central dogma is transcription, during which DNA nucleotides are transcribed into RNA nucleotides. The second step, translation, involves the conversion of RNA nucleotides to amino acids and eventually proteins. In summary, the central dogma of life is DNA to RNA to protein.

Unfortunately, things aren’t always that simple, and such is the case of retroviruses. Retroviruses are a group of viruses that use a process different from what the central dogma states; the most famous retrovirus is the human immunodeficiency virus (HIV). HIV then causes acquired immunodeficiency syndrome (AIDS). Like all viruses, retroviruses consist of an RNA genome contained in a protein capsid shell and a lipid envelope.

The way a retrovirus hijacks and takes over a cell is reverse transcription. When it invades a host cell, the virus produces an enzyme called reverse transcriptase. Reverse transcriptase converts viral RNA into proviral DNA: a crucial step for the upcoming phases. Using the enzyme, integrase, the newly assembled proviral DNA is then inserted into the host DNA.

After the new viral DNA is incorporated into the host DNA, transcription and translation occur. The genes on the DNA code for viral proteins continue to get manufactured. Once there are enough copies of virus proteins and particles, they combine and more fresh viruses assemble. Soon enough, the mass amounts of viruses break through the host’s cell membrane and kill the cell. The cycle then repeats again with another cell.

The central dogma of molecular biology states that DNA goes from RNA to protein and such laws are not easily broken, but retrovirus is definitely an exception, making DNA from RNA.

 

Citations:

“What Is the 'Central Dogma'?” Facts, The Public Engagement Team at the Wellcome Genome

Campus, 25 Jan. 2016, www.yourgenome.org/facts/what-is-the-central-dogma.

“Reverse Transcriptase.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.,

www.britannica.com/science/reverse-transcriptase.

Boundless. “Boundless Biology.” Lumen, courses.lumenlearning.com/boundless

biology/chapter/virus-infections-and-hosts/.

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