Apuntes sobre micro biologia en ingles

Páginas: 36 (8863 palabras) Publicado: 31 de agosto de 2010
The next thing is Transcriptional control. The Gene is on. Its function is to transcribe a protein. The question is how many messages and what type should I make? We are controlling how many we produce or transcribe. The TATA box alone can only produce 10-30 mRNA per minute. This is okay for the housekeeping genes. When we need to make proteins in amplitude or suddenly a big amount we have a 6-10base pairs called an enhancer we find them away from the TATA box and from the gene itself. Enhancers are attached to a gene but are located a long distance away. To this enhancer binds a protein called the enhancer binding protein. This speeds up production. Enhancers are in those proteins that need to bulk produce at a high speed. Housekeeping genes do not have them. They only have a TATA box.So now the DNA is going to bend or loop such that the TATA box is going to align itself directly below the enhancer. The RNA polymerase comes in and a conformation change will occur and the speed and amount will increase. The e.b.p caused a change in the RNA polymerase. The RNA polymerase is the same but there is a change in molecule and the RNA polymerase runs at a much higher speed.

Theopposite of enhancers are silencers. They shut down the production. Similarly the silencers bind to the RNA polymerase and they silence the production.

Second type is combinatorial control. It is also enhancer base. The majority of our genes don’t have just one enhancer. The more enhancers you have the more mRNA production. Or you can have selective production. The numbers can be multiplieddepending on how many enhancers you got. DNA regulators are the enhancers. They are called this because they manipulate the DNA to have the best production.

Say you have a liver cell and a kidney cell they both have the same genes. In the liver cell protein 1, 2 and 3 are DNA regulators that turn on the gene. On the kidney cell only protein 1 is bound. This means that you have a lower production. Youare still producing the same messages just in a different amount. If the silencer protein is present the whole system is going to shut off. Even if the enhancer proteins are there the silence dominates over the enhancers. Here we are talking about fine-tuning of euchromatic genes.

The last one is the coordinated (simultaneous) control. Let’s say that the same gene at the same time needs to beturn on. You are going to simultaneously control the same gene in different parts of the body. The genes are going to be control by hormones. Let’s say you have a liver cell, a kidney cell, a neuron cell, and a cardiac cell. They are all open but you don’t want it on in the cardiac cells. Hormones control all varieties of genes. Those cells that need the hormone have receptors. Hormone X turns ongene A. Those that have the receptor pick up the hormone. Even though the Gene A is opened in the cardiac cell it does not have a receptor and does not turn on the gene.

Receptor mediated endocytosis take places. The receptor binds to the hormone and the whole thing comes into the cell.

Zoom into the cells. The receptor and the hormone complex together make their entrance into the DNA. Thereceptor and the hormone bind to the response element. Each hormone has its own response element. About 6-10 b.p. like the enhancer should have a piece of sequence that response to the particular hormone. The whole complex sits on the response element and the production is turn on. All endocrine systems control genes. The job of the response element is to turn on the gene only when the requiredhormone is present if the hormone is not their there might be production but it is not very much. The hormone makes the production go up.

So let’s say we have made the message but don’t want to use it until some hours later. Post-transcriptional control comes in. the message is made in the nucleus. The way to prevent translation is to prevent the message to send the message into the cytoplasm....
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