Bacterial And Viral Gene Regulation

Gene regulation is the way genes are expressed, and it starts with the central dogma. Gene regulation starts with the DNA which makes mRNA which then makes proteins. Prokaryotes, which are bacteria (for example E. coli), eat whatever we eat; therefore, if we drink milk, the bacteria will break down the lactose using gene regulation (Anderson, 2011). Bacterial genes are found in operons and use regulatory proteins to turn on and off groups of genes in reaction to many environmental changes. In bacteria, the gene expression is effective for gene information and it depends on complex regulatory mechanisms that have control over transcription. Regulatory gene expression can have either positive or negative control and can be inducible or repressible (Klug, Cummings, Spencer, Palladino, & Killian, 2018).

Bacteria which have a circular DNA, have genes that are usually found in operons that are transcribed as a group but have only one promoter in a sense region that starts on the five prime ends. Each operon has a regulatory DNA sequence allowing coordinated expression (Garrett & Grisham, 2016). Regulatory proteins work with operators to control the transcription of the genes. An inducible operon increases synthesis of the gene expression and the repressible operon decreases synthesis of the gene being expressed.

Bacteria have three genes that are used for regulation and all of them deal with lactose, so they are called the lac operon. In the lac operon, there are three genes: the lac Z, lac Y, and lac A and they all have a common promoter and operator. The operator works as an on and off switch, regulating if the gene is on or not (Anderson, 2011). There is also a repressor and if lactose is absent, the repressor binds to the operator preventing RNA polymerase from being transcribed. In the presence of lactose, the sugar will be converted into allolactose binding it to the repressor and changing its conformation not allowing the repressor to bind to the operator (Garrett et. al., 2016). Then, the RNA polymerase binds to the operon promoter because there is no more repressor making mRNA for each gene transcribed and each lac gene will be translated into protein. Finally, each protein will break down the lactose and when the bacteria finish breaking down the lactose the repressor binds again to the operator. So, when there is lactose present, we call it positive control. A negative control is when tryptophan synthesizes the genes to be transcribed. Whenever tryptophan is bound to the repressor, RNA polymerase is blocked and does not get transcribed. However, if there is no tryptophan present, the repressor changes its conformation and unbinds from the operator allowing RNA polymerase to make proteins which will make more tryptophan.

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Viruses require the use of host cells in order to thrive. They can affect genes by binding to healthy cells and taking over the cells by inserting its own DNA into the cells, stopping the cell’s normal production and instead creating additional viral genetic materials and proteins. Viruses can stay inactive within their host cells for a long time without any apparent effects, known as the lysogenic phase. However, when an inactive virus is activated, it goes into the lytic phase. During the lytic phase, viruses start to replicate until they overload the host cell. Because the host cell is overloaded it ends up being killed and the virus subsequently moves on to other host cells where the cycle is continued.

Viruses have two different cycles and can either have RNA or DNA, different from bacteria that have both DNA and RNA. In the lytic cycle, for example, the retrovirus (or cold virus) inserts its genetic material in the host cell which goes into the cell’s nucleus and makes more copies of its own DNA, this is called DNA replication. These DNA copies are transcribed into mRNA, which gets into the ribosomes translating into proteins. Then the virus breaks the cells spreading to other cells. RNA viruses will have RNA instead of DNA and will insert its RNA into the cell doing reverse transcriptase which will turn RNA into DNA and cause mutation.

Viruses can also replicate through the lysogenic cycle; the lysogenic cycle creates a lytic cycle. In the lysogenic cycle, the virus will insert its DNA to the bacteriophage and when the bacteria replicate, it will keep replicating, this is how herpes virus replicates and does not get away from the body. Because it can replicate over again. Therefore, the main difference between a viral and a bacterial regulation is because a virus invades a host cell while bacteria have their own cellular mechanism and can be good or bad. The virus makes genetic material copies from its host cell to replicate, releasing new particles destroying its host cell. Also, viruses can have either DNA or RNA, while bacteria have both DNA and RNA.