Types of DNA Microarray

Microarrays experiments has been classified into three basic types based on the sample which the two types grouped in genomics while the others is “transcriptomic”, means that this kind of array measure the level of mRNA. The different between this microarray are the types of immobilized DNA used to generate the arrays and also the different kind of information or results obtained from chips.

Types of transcriptomic

Changes in Gene Expression Levels

In this case, determination level or volume of certain gene expression called “microarrays expression analysis” and the arrays used in this types called “ expression chips” .The immobilized DNA used is cDNA derived from mRNA of known gene. The sample and control cDNA hybridize to the chips derived from normal and diseased tissue. If the sample cDNA (derived from diseased tissue) is over expressed than the normal cDNA, then when fluoresce applied to chips, its show that there will be more red fluoresce intensity than the green one. This kind of microarrays used to drug development, drug responds, therapy development and disease diagnosis. For examples certain genes is over expression in a particular form of cancer, then researchers can use expression chips to see a new drugs that would reduce over expression and force the cancer into remission.


Types of genomics

Genomic Gains and Losses

Researchers use a technique called microarray Comparative Genomic Hybridization (CGH) to look for genomics gain or loses in certain types of disease gene or for a changes in copy number of particular gene involved in diseased. In microarray CGH, the large pieces of genomics DNA is our target and in the hybridization mixture contain fluorescently labeled DNA obtained from normal (control) and diseased tissue. Therefore, if the copy of target gene has increased, the sample DNA would hybridize on the spot greater than control DNA o n the spot. As a results, spot containing high intensity of red fluoresce then green fluoresce and this showed that the copy number of diseased number has increased. This kind of arrays used in tumor classification, risk assessment, prognosis prediction,

Mutations in DNA

This types of mutation microarrays analysis is used by researchers to detect mutation or polymorphisms in gene sequences,the target or immobilized DNA. In this case, the target gene placed in given spot within the arrays but differs from other spots in same microarrays by put one or a few specific nucleotide. In this analysis the immobilize DNA is sequence known as Single Nucleotide Polymorphisms or SNP (a small genetics changes in a person DNA sequences). These microarrays different from the expression and CGH microarrays because it only needs DNA control samples in hybridization solution. When genomic DNA from a individual is hybridized to an array loaded with SNPs, then the sample would only hybrid to its specific SNPs of that person and the fluoresce applied showed that the color intensity indicate that person either in risk or not.