Often the amount of data generated by gene chip analysis is overwhelming. Conventional genomic analysis involves the description of the position of genes on chromosomes and does not per se lead to functional insights into cell or tissue function. However, gene arrays allow for the simultaneous measurement of all transcribed RNA, and hence of all active genes, in any one state of activity or differentiation. This pattern of mRNA expression is termed an expression profile. The collective constellation of proteins that are selectively and differentially expressed in a cell or tissue is a critical determinant of its structure or function. There are many possible applications for the analysis of this profile; for example, transcripts that are cell-type specific or possess a cell type-specific response to a particular stimulus can be identified.
DNA array analysis permits the organization of expressed genes into clusters based on their differential expression patterns. For example, a large number of whole-genome observations in the yeast cell have been compared using several different experimental conditions and a template in which many thousands of measurements can be conveniently displayed. This model takes advantage of the fact that color-coded probes were hybridized to the array, and that the intensity of the color is directly correlated with expression levels of the different transcripts. Based on the relative intensity of expression of each gene, genes are clustered in hierarchies based on their similarities and differences in expression across the various experiments, for example in relation to cell cycle regulation. Such tabulations allow unforeseen correlations to take place. Grouping genes according to known function may also help the functional interpretation of the results, especially when a gene identified has been little studied, and hence the total functions of the gene in question may not be fully appreciated. These analyses may be facilitated by computer programs and algorithms especially designed for these applications.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.