Genetics: Gene Expression - Genes And Noncoding Dna, Flow Of Genetic Information, Control Of Gene Expression, Gene Expression And Aging
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Genomes contain all the genetic information needed by an organism, regardless of the circumstance or environment. Generally, however, even single-cell organisms use only a fraction of their genome at any time; that is, cells generally express only a fraction of their genome at any given time. This is especially true among the individual cells that make up multicellular organisms, where cell specialization (differentiation) dictates that only certain genes be expressed in certain cells, and only at particular times during the organism's life span.
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In most organisms, genes are composed of discrete segments of DNA. Genes code for all of the proteins and structural RNA molecules used by cells within an organism. The coding segments of genes are often flanked by segments, or elements, that provide regulatory information. Regulatory elements control gene expression— the process that produces a functional protein or RNA molecule from the e…
Gene expression is controlled at multiple levels, including transcription (initiation and elongation), posttranscriptional processing, RNA stability, RNA export and association with ribosomes, translation (initiation and elongation), and posttranslational processing. Each level tends to be highly regulated and complex. Moreover, each level requires the cooperation of both general and cell-type-spe…
Age-dependent changes in the expression of specific genes have been found in virtually all organisms and tissues that have been tested. These changes have been found to occur at all levels, ranging from the initiation of gene transcription to the posttranslational modification of proteins. In many cases, it has been difficult to decipher which changes in gene expression are responsible for aging p…
No single change in gene expression has yet been shown to be responsible for limiting or extending the life span of an organism (or even a tissue, for that matter). However, manipulation of general regulators of gene expression has been shown to alter life span, at least in model organisms. Perhaps the best example of this is the SIR2 protein, which is conserved from yeast to mammals and is respon…
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about 1 month ago
virtually all organisms and tissues that have been tested. These changes have been found to occur at all levels, ranging from the initiation of gene transcription to the posttranslational modification of proteins. In many cases, it has been difficult to decipher which changes in gene expression are responsible for aging p…