CHIPS USED IN MICROARRAY MACHINE IN HOSPITALS

Chips used in MICROARRAY

A DNA chip is a solid surface to which are attached a series of DNA fragments. Surfaces used to fix the DNA are highly variable and may be glass, plastic and even silicon. DNA chips are used to analyze the differential expression of genes, monitor levels of thousands of them simultaneously. (Staudt 2000, 503-511)

Its operation is basically to measure the level of hybridization between the specific probe ("probe" in English), and the target molecule (target), generally indicated by fluorescence and analyzed by image analysis, which indicates the level gene expression.

It is often used to identify genes with differential expression under different conditions. For example, to identify genes that cause certain diseases by comparing expression levels between healthy cells and cells that is developing certain types of diseases. (Kulesh 1999, 8453-8457)

Historical Background

The DNA chip technology comes from a widely used technique in molecular biology, the Southern blot. The pre-genomic biology studied individual genes, one by one, so that it could study it thoroughly. What characterizes the post-genomic era is not measurable, but the number of simultaneous measurements that can be performed. To meet this objective and to study many genes at once took a change of paradigm with the same resources; get an image of lower resolution but with a more general perspective.

DNA chips are manufactured using a variety of technologies. The great development of this technique has come to normalize the use of robots that handle most of the process of handling chips (synthesize the DNA template that binds to the chip, join, add reagents, etc.). (Fornace 1999, 3666-3672)

DNA chips can be used to detect RNA, which may or may not be translated into proteins. Scientists refer to this kind of analysis as "expression analysis" or "transcriptome analysis." Retrotranscribir usually RNA to DNA in these cases, so that we use in the sample is cDNA.

Using DNA chips to study the expression of different genes was published in 1995, in the prestigious scientific journal Science and the first body eukaryote with the whole genome (Saccharomyces cerevisiae) arranged in a DNA chip was released in 1997 in the same journal

Types

In this type of DNA chips (microarrays Spotted English) tests are Oligonucleotide, complementary DNA (cDNA) or small pieces of chain reaction of polymerase, which correspond to messenger RNA (mRNA). In this type of DNA chip hybrid cDNA two conditions that are marked, each of these conditions with two different fluorophores. (Barry 2000, 221-231)

Conditions are mixed and hibridades in the same DNA chip. In this way you can see genes that are activated or repressed under different conditions. The counterpart of these experiments is that absolute levels can be observed in the expression and qPCR required for all quantitive analysis.

Oligonucleotide DNA chips

In DNA chips or micromarreglos oligonuleótidos single channel tests are designated parts of a sequence known or predicted mRNAs. These chips DNAs give estimates of expression level, but different conditions cannot be observed in the same array, so ...