Genes are important to every organism (organism referring to eukaryotes and prokaryotes). All the genes in your body possess characteristics that help define an organism, but these characteristics are not always active. The process of making these characteristics active (or functional) is called gene expression.
What is Gene Expression?
Gene expression refers to how genes are converted into a substance that can be further used by the body. In most cases, this product is in the form of proteins; however, there are also times that non-protein substances are being converted. This process somehow differs depending on the kind of cell.
As you probably know, there are two kinds of cells – prokaryotes and eukaryotes. Prokaryotes are single-celled organisms that do not have a nucleus. So, the DNA that is normally found in a nucleus can be found around the cytoplasm instead. On the other hand, eukaryotes are intracellular organelles that have a nucleus. For this type of cell, you will find the DNA inside the nucleus itself.
Transcription and Translation
Before fully understanding how gene expression is controlled in prokaryotes, it would help to know what transcription and translation mean. Both are the primary processes involved in gene expression.
First, transcription is the conversion of DNA into a complementary RNA code. This is done so that DNA can easily be converted into a useful kind of protein so that several functions of a cell can be done. The end product of transcription is mRNA, but tRNA and rRNA can also be products depending on the kind of function needed to be done by a cell.
Second, translation is the actual conversion of the now converted rRNA into a protein. tRNA is used to convert mRNA into a protein. The conversion of mRNA to a protein is actually similar to that of a technical matching. This is because the mRNA has a code that the tRNA reads and the code is attached to a certain amino acid matching the first three letters (codon) found int he mRNA. Once the tRNA identifies the kind of amino acid to be produced, the amino acid binds to the mRNA.
Gene Expression in Prokaryotes
Now that you know what is involved in gene expression and what the whole process is, it’s time to understand how it occurs in prokaryotes.
Prokaryotes have no nucleus, so naturally, its DNA floats around the cytoplasm. When the cell is in need of a certain function, this is the only time when transcription starts. Gene expression does not occur when the cell does not need it so that the cells can save on energy. For prokaryotes, both transcription and translation happen simultaneously and both occur in the cytoplasm.
Gene expression is also regulated. There are certain mechanisms that tell the prokaryote to “turn off” when there is no protein needed. This is why gene expression is controlled. The control of gene expression in prokaryotes is also influenced by the environment of the cell. If the cell has enough nutrients that enable a conversion of DNA to mRNA, the gene expression can be done.