Scientists continue today to conduct large-scale population studies - for example, to determine how often individuals with a particular mutation actually develop breast cancer, or to identify the changes in gene sequences that are most often associated with particular diseases.
This has become possible because, just as is the case for computer chips, very large numbers of 'features' can be put on microarray chips, representing a very large portion of the human genome. Microarrays can also be used to study the extent to which certain genes are turned on or off in cells and tissues.
Today, DNA microarrays are used in clinical diagnostic tests for some diseases. Sometimes they are also used to determine which drugs might be best prescribed for particular individuals, because genes determine how our bodies handle the chemistry related to those drugs.
With the advent of new DNA sequencing technologies, some of the tests for which microarrays were used in the past now use DNA sequencing instead. But microarray tests still tend to be less expensive than sequencing, so they may be used for very large studies, as well as for some clinical tests.
To determine whether an individual possesses a mutation for a particular disease, a scientist first obtains a sample of DNA from the patient's blood as well as a control sample - one that does not contain a mutation in the gene of interest.
The researcher then denatures the DNA in the samples - a process that separates the two complementary strands of DNA into single-stranded molecules. At any given moment, each of our cells has some combination of these genes turned on, and others are turned off.
How do scientists figure out which are on and which are off? Scientists can answer this question for any cell sample or tissue by gene expression profiling, using a technique called microarray pronounced MY-crow-ah-ray analysis. Microarray analysis involves breaking open a cell, isolating its genetic contents, identifying all the genes that are turned on in that particular cell, and generating a list of those genes.
DNA microarray analysis is a technique that scientists use to determine whether genes are on or off. A DNA micorarray allows scientists to perform an experiment on thousands of genes at the same time. The contents provided here are solely the responsibility of the authors and do not necessarily represent the official views of NIH.
DNA Microarray. Microarray Analysis. Scientists know a gene is on in a cell if its mRNA is present. One can analyze the expression of many genes in a single reaction quickly and in an efficient manner.
DNA Microarray technology has empowered the scientific community to understand the fundamental aspects underlining the growth and development of life as well as to explore the genetic causes of anomalies occurring in the functioning of the human body.
A typical microarray experiment involves the hybridization of an mRNA molecule to the DNA template from which it is originated. Many DNA samples are used to construct an array. The amount of mRNA bound to each site on the array indicates the expression level of the various genes.
This number may run in thousands. All the data is collected and a profile is generated for gene expression in the cell.
An array is an orderly arrangement of samples where matching of known and unknown DNA samples is done based on base pairing rules. An array experiment makes use of common assay systems such as microplates or standard blotting membranes. The sample spot sizes are typically less than microns in diameter usually contain thousands of spots. Thousands of spotted samples known as probes with known identity are immobilized on a solid support a microscope glass slides or silicon chips or nylon membrane.
These are used to determine complementary binding of the unknown sequences thus allowing parallel analysis for gene expression and gene discovery. An experiment with a single DNA chip can provide information on thousands of genes simultaneously. An orderly arrangement of the probes on the support is important as the location of each spot on the array is used for the identification of a gene. Depending upon the kind of immobilized sample used construct arrays and the information fetched, the Microarray experiments can be categorized in three ways:.
The sample has genes from both the normal as well as the diseased tissues.
0コメント