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Although some aspects of microbiology are similar between prokaryotes and eukaryotes, gene regulation differs between the two. Gene regulation in eukaryotes is much more complex, simply because eukaryotes are more complex than prokaryotes. Often times, genes within eukaryotes are naturally found "off". Within eukaryotes, there are four levels of DNA regulation.
1. Transcription
DNA within eukaryotes is found as chromatin wrapped around histones, which creates the chromosomes. When the chromatin is wrapped around the histones, the proteins that need to interact with the base pairs is not able to - meaning that the gene is not expressed. In order for these genes to be expressed, the histones must interact with various signals, which loosens the interactions between the histone and chromatin, allowing proteins to unwind the DNA (a process that is necessary for gene expression). The signals that a cell receives are due to the environment that the cell is exposed to. A specific protein (ligand) binds to a receptor on the surface of the cell, which causes a cascade of events that results in certain genes to be expressed. As a result of the signals, the target area of DNA is unwound and transcription factors (TFs) recognize a 6-10 base pair motif in the DNA and that is where the TFs can bind. If the cell does not receive the specific signals for the chromatin to loosen away from the histone and unwind, the chromatin will remain tightly wound around the histone and the gene will not be accessible for the TFs (Hoopes, 2008).
1. Transcription
DNA within eukaryotes is found as chromatin wrapped around histones, which creates the chromosomes. When the chromatin is wrapped around the histones, the proteins that need to interact with the base pairs is not able to - meaning that the gene is not expressed. In order for these genes to be expressed, the histones must interact with various signals, which loosens the interactions between the histone and chromatin, allowing proteins to unwind the DNA (a process that is necessary for gene expression). The signals that a cell receives are due to the environment that the cell is exposed to. A specific protein (ligand) binds to a receptor on the surface of the cell, which causes a cascade of events that results in certain genes to be expressed. As a result of the signals, the target area of DNA is unwound and transcription factors (TFs) recognize a 6-10 base pair motif in the DNA and that is where the TFs can bind. If the cell does not receive the specific signals for the chromatin to loosen away from the histone and unwind, the chromatin will remain tightly wound around the histone and the gene will not be accessible for the TFs (Hoopes, 2008).
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2. Post-Transcription
Once mRNA has been made, there are some steps that it goes through, which enables the mRNA to leave the nucleus and undergo the process of translation within the cytoplasm. These modification that are essential to the mRNA being transported out of the nucleus include:
- intron excising
- extron splicing
- 5'- end Guanine rich cap
- 3'- end poly A tail
These modifications ensure that the mRNA is not degraded when it moves to the cytoplasm and it also removes the portions of RNA that do not code for the protein that needs to be created.
Without these modifications, the mRNA will be degraded in the cytoplasm, which means that the protein will not be created.
Once mRNA has been made, there are some steps that it goes through, which enables the mRNA to leave the nucleus and undergo the process of translation within the cytoplasm. These modification that are essential to the mRNA being transported out of the nucleus include:
- intron excising
- extron splicing
- 5'- end Guanine rich cap
- 3'- end poly A tail
These modifications ensure that the mRNA is not degraded when it moves to the cytoplasm and it also removes the portions of RNA that do not code for the protein that needs to be created.
Without these modifications, the mRNA will be degraded in the cytoplasm, which means that the protein will not be created.
3. Translational
Once the mRNA has been modified and moved to the cytoplasm, it is translated into a long string of amino acids that fold and create the protein that the cell needs. The mRNA that was translated can then be reused or recycled, meaning that it can be translated into protein again or degraded and recycled. The conditions within the cell dictate which of the two potential scenarios occur. Various signals within the cell regulate the processes that occur.
Once the mRNA has been modified and moved to the cytoplasm, it is translated into a long string of amino acids that fold and create the protein that the cell needs. The mRNA that was translated can then be reused or recycled, meaning that it can be translated into protein again or degraded and recycled. The conditions within the cell dictate which of the two potential scenarios occur. Various signals within the cell regulate the processes that occur.
4. Post-Translational
Once the protein has been made, there are modifications that occur, which either activate the protein or allow it to transport to the area of the cell where it is needed. If these modifications do not occur, the protein is inactive and therefore useless.
Once the protein has been made, there are modifications that occur, which either activate the protein or allow it to transport to the area of the cell where it is needed. If these modifications do not occur, the protein is inactive and therefore useless.
Reference:
SBI4U: Biology, Grade 12, University Preparation, Unit 3: Molecular Genetics, Activity 4: Protein synthesis control mechanism. Obtained from: https://download.elearningontario.ca/repository/1225700000/SBI4UCU03A04/content.html
SBI4U: Biology, Grade 12, University Preparation, Unit 3: Molecular Genetics, Activity 4: Protein synthesis control mechanism. Obtained from: https://download.elearningontario.ca/repository/1225700000/SBI4UCU03A04/content.html