The video describes how epigenetic regulation controls the expression of genes.
Like prokaryotic cells, the transcription of genes in eukaryotes requires the action of an RNA polymerase to bind to a DNA sequence upstream of a gene in order to initiate transcription.
The prokaryotic cells require other factors to initiate transcription.
It is not possible to initiate transcription in eukaryotic cells by itself.
General transcription factors bind to the core promoter region in order to assist with the binding of RNA polymerase.
Specific transcription factors bind to various regions outside of the core promoter region and interact with the proteins at the core promoter to enhance or suppress the activity of the polymerase.
The control of genes is easier with organized genes.
The coding sequence is upstream of the promoter region.
This region can be short or long.
The longer the promoter, the more space is available for binding.
More control is added to the process.
The length of the promoter can be different between genes.
The level of control of genes can be very different.
The core promoter region contains 25 to 35 bases upstream of the start site.
The box has a consensus sequence.
The binding site for the TFIID complex is the TATA box.
Other transcription factors are recruited by the binding of TFIID.
There are other binding sites in the promoter.
Some biologists prefer to restrict the range of the promoter to the core promoter, and refer to these additional sites as promoter-proximal elements, because they are usually found within a few hundred base pairs upstream of the transcriptional start site.
The CAAT box has the consensus sequence 5'-CCAAT-3' and the GC box has the consensus sequence 5'GGGCGG-3'.
These promoter-proximal elements can be regulated by specific transcription factors.
A given gene may have its own combination of binding sites.
There are hundreds of transcription factors in a cell.
Environmental stimuli cause the transcription factors to find their binding sites and initiate the transcription of the gene that is needed.
There are additional regions in some genes.
They can be found in the coding region of the gene or thousands of nucleotides away.
There are enhancer regions for specific transcription factors.
Since the enhancer region is distant from the promoter, the DNA must bend to allow the two sites to come into contact.
The shape change allows for the interaction of the specific activator proteins bound to the enhancers with the general transcription factors bound to the promoter region.
An enhancer is a sequence of genes.
The enhancers are made up of short genes called control elements.
Activators bound to the control elements interact with transcription factors.
Two genes may have the same promoter but different control elements.
Eukaryotic cells have mechanisms to prevent transcription.
There are transcriptional repressors that can bind to promoter or enhancer regions.
Suppressors respond to external stimuli to prevent the binding of transcription factors.
By the end of this section, you will be able to understand and explain the role of RNA in regulating gene expression.
Post-transcriptional modification is the process that takes place after an RNA molecule has been transcribed.
The post-transcriptional step can be regulated to control the expression of genes in the cell.
Noprotein will be created if the RNA is not processed, shuttled, or translated.
There are regions in the transcript that are removed prior to translation.
The introns are removed prior to the translation of an RNA molecule after it has been transcribed.
Pre-mRNA can be used to create different types of proteins.
In the 70s, genes were first observed to have alternativeRNAS.
When different combinations of exons are combined to form the mRNA, alternativeRNAS is a mechanism that allows different products to be produced from one gene.
More often than not, this alternative splicing is controlled by the cell and used as a way to control the production of different products in different cells or at different stages of development.
70 percent of genes in humans are expressed through alternative splicing, according to one estimate.
The order of the exons is always the same.
A transcript with exons 1 2 3 4 5 6 7 or 1 2 3 6 7, but never 1 2 5 4 3 6 7, is called a transcript with exons 1 2 3 4 5 6 7 or 1 2 3 6 7, and is called a transcript with exons 1 2 3
There are five basic ways to do alternative splicing.
Introns have a beginning- and ending-recognition sequence; it is easy to imagine the failure of the splicing mechanism to identify the end of an intron and instead find the end of the next intron, thus removing two introns and the intervening exon.
There are mechanisms in place to prevent intron skipping, but they are likely to fail.
It's more than likely that the "mistakes" will produce a nonfunctional protein.
It is possible that alternative splicing could create a new variant of the original one without the loss of the original one.
Gene duplication has helped in the evolution of new functions by providing genes that may evolve without eliminating the original, functional proteins.
Amelanistic snakes have only red and yellow colors on their skin.
The cause of amelanism in these snakes is the addition of a transposable element into an intron.
In this video, you can see the process in action.
The ends of the strand are protected by two protective "caps" before it leaves the nucleus.
The 5' and 3' exonucleases can degrade the RNAs.
The GTP is placed on the 5' end of the mRNA so that the 5' carbons of the GTP and the terminal nucleotide are linked.
The two ends of the RNA are protected.
The length of time that the RNA resides in the cytoplasm can be controlled once theRNA is transported to the cytoplasm.
The lifespan of each molecule is defined by the rate at which it decays.
The rate of decay can affect how much is in the cell.
The time available for translation of the mRNA will be shortened if the decay rate is increased.
If the rate of decay is reduced, the mRNA molecule will reside in the cytoplasm longer and more can be translated.
The rate of decay is referred to as the stability.
For longer periods of time, the RNA will be detected if it is stable.
The stability of the RNA can be influenced by the binding of genes to it.
They are not introns.
These are regions that regulate the translation of genes.
Depending on the specific RBP that is binding, the stability of an RNA molecule can be increased or decreased.
There are 5' and 3' untranslated regions behind theprotein-coding region.
At the 5' or 3' UTR, the stability of the RNA molecule is influenced.
Other elements called microRNAs can bind to the RNA molecule and bind to RBPs.
The long pre-miRNAs are made in the nucleus.
By the end of this section, you will be able to understand the process of translation and discuss its key factors.
The control of this process is dependent on theRNA molecule.
The stability of the RNA will have a big impact on the translation of the molecule.
The amount of time available for translation changes with the stability.
The process of translation is similar to the process of transcription.
The translation is initiated by binding the met-tRNAi to the 40S ribosome.
The 40S ribosome is binding to the tRNA-eIF2-GTP complex.
There are several different initiation factors that recognize the 5' cap of the mRNA and the poly-A tail of the same mRNA.
The ribosome scans the mRNA until it finds a start and then it stops.
If eIF-2 is phosphorylated, it can't bind to GTP.
The initiation complex can't form properly and translation is impeded.
The initiation complex can form normally if eIF-2 remains unphosphorylated.
Patients with Alzheimer's, Parkinson's, and Huntington's have seen an increase in the levels of eIF-2.
The addition of groups such as acetyl and ubiquitin can be used to modify the genes.
The activity of these groups is regulated by the addition or removal of these groups.
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