How is gene expression controlled

Growth factor signaling is complex and involves the activation of a variety of targets, including both transcription factors and non-transcription factor proteins. Alcohol dehydrogenase. Cooper, G.

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To understand how gene expression is regulated, we must first understand how a gene codes for a functional protein in a cell. The process occurs in both prokaryotic and eukaryotic cells, just in slightly different manners.

Prokaryotic organisms are single-celled organisms that lack a cell nucleus, and their DNA therefore floats freely in the cell cytoplasm. To synthesize a protein, the processes of transcription and translation occur almost simultaneously. When the resulting protein is no longer needed, transcription stops.

As a result, the primary method to control what type of protein and how much of each protein is expressed in a prokaryotic cell is the regulation of DNA transcription. All of the subsequent steps occur automatically. When more protein is required, more transcription occurs. Therefore, in prokaryotic cells, the control of gene expression is mostly at the transcriptional level.

Eukaryotic cells, in contrast, have intracellular organelles that add to their complexity. The newly synthesized RNA is then transported out of the nucleus into the cytoplasm, where ribosomes translate the RNA into protein.

The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm. First, an enzyme nicknamed "Dicer" chops any double-stranded RNA it finds into pieces that are about 22 nucleotides long.

This binding blocks translation of viral proteins at least partially, if not completely. The RNAi system could potentially be used to develop treatments for defective genes that cause disease. The treatment would involve making a double-stranded RNA from the diseased gene and introducing it into cells to silence the expression of that gene. All Rights Reserved. Date last modified: February 2, Created by Wayne W.

DNA, Genetics, and Evolution. Contents All Modules. Control of Gene Expression By gene expression we mean the transcription of a gene into mRNA and its subsequent translation into protein. The structural genes contain the code for the proteins products that are to be produced. Regulation of protein production is largely achieved by modulating access of RNA polymerase to the structural gene being transcribed.

The promoter gene doesn't encode anything; it is simply a DNA sequence that is initial binding site for RNA polymerase. In vivo footprinting analysis of the human beta globin promoter shows that adult erythroblasts E, lane 4 have footprints on important regulatory motifs note lighter regions, especially at CACC as compared to the other samples.

Of these cells lines, none is part of the lineage leading to red blood cells. Genomic footprinting and sequencing of human beta-globin locus: tissue specificity and cell line artifact. All rights reserved. The Role of Chromatin.

Multiple Interactions Provide Synchronous Control. References and Recommended Reading Pulverer, B. Journal of Biological Chemistry , — Remenyi, A.

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