Prokaryotic cells lack organelles and have free-floating DNA and RNA. Prokaryotic transcription is controlled by RNA polymerase, which initiates transcription at the promoter site and creates unusable transcripts before continuing. The strength of the binding between RNA polymerase and DNA is related to the consensus sequence. Transcription occurs at about 40 nucleotides per second and can be disrupted by RNA sequences or specific proteins.
Unlike eukaryotic cells, a prokaryotic cell such as a bacterium generally does not have individual structures called organelles within it. There is usually no nucleus, mitochondria, or other area where separate metabolic processes occur; everything is mostly free-floating within the cell wall and plasma membrane. Like eukaryotic cells, there are usually deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) strands that can be copied through transcription. Prokaryotic transcription is typically controlled by an enzyme called prokaryotic RNA polymerase, which has to initiate the transcription of DNA, while the termination of the process is usually triggered by other nucleotide sequences.
When the enzyme RNA polymerase travels the length of a DNA strand, it unravels it at the transcription site, and messenger, transfer, and ribosomal RNA can be produced. There are typically two types of the enzyme in prokaryotic transcription; one is a central enzyme that can make copies but cannot find the appropriate site on a gene. A holoenzyme form of the molecule is often capable of initiating transcription in the specific region, and thus is designed to locate the promoter sequences that tell the molecule when to start copying DNA. The holoenzyme performs this function through a component called sigma.
Prokaryotic transcription begins when RNA polymerase attaches to the promoter site of the DNA. The molecule and the double-stranded structure, called a closed complex, can then interact and the DNA is opened into a single-stranded sequence near where transcription begins. This is called an open complex. The enzyme typically initiates the transcription process by creating about 10 unusable transcripts, which are prevented by a protein from leaving the complex.
Once this protein is released, the enzyme continues with the transcription. There are sometimes differences in the strength with which RNA polymerase and proteins bind to DNA; the strength of this link can be related to the statistical probability that a certain base is located in a given location. How closely the bases match this consensus sequence often determines how strong the binding will be.
Prokaryotic transcription of RNA usually occurs at about 40 nucleotides per second. Some proteins can change how fast this happens, and the copy speed of certain sequences can also be different. Regulatory genes often change how sequences are expressed depending on what the cell needs. Prokaryotic transcription can be disrupted either when sequences in the RNA cause the molecular complex and DNA to separate, or when a specific protein binds to and travels to the enzyme RNA polymerase.
Protect your devices with Threat Protection by NordVPN
