what is the principal working behind gene microarrays

Asked by mehdi.moledina | 30th Jul, 2016, 07:33: PM

Expert Answer:

A DNA microarray also commonly known as DNA chip or biochip is a collection of microscopic DNA spots attached to a solid surface. The DNA microarray or gene microarray is a tool used to determine whether the DNA from a particular individual contains a mutation in genes.

Principle:

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). The spots can be DNA, cDNA, or oligonucleotides. These are used to determine complementary binding of the unknown sequences thus allowing parallel analysis for gene expression and gene discovery.

Procedure:

  • To determine whether an individual possesses a mutation for a particular disease, 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 is obtained.
  • The DNA in the samples is then denatured, a process that separates the two complementary strands of DNA into single-stranded molecules.
  • The long strands of DNA are cut into smaller fragments.
  • The fragments are labelled by attaching a fluorescent dye. The patient’s DNA is labelled with green dye and the control DNA is labelled with red dye.
  • Both sets of labelled DNA are then inserted into the chip and allowed to hybridize or bind to the synthetic DNA on the chip.
  • If the individual does not have a mutation for the gene, both the red and green samples will bind to the sequences on the chip that represent the sequence without the mutation.
  • If the individual does possess a mutation, the individual's DNA will not bind properly to the DNA sequences on the chip that represent the "normal" sequence but instead will bind to the sequence on the chip that represents the mutated DNA.

Answered by Sheetal Kolte | 1st Aug, 2016, 10:25: AM