Biotechnology: Processes

Microarrays

Contributors

Ben Whitten

tutorial.png

one.png
What is a microarray?
Slide1.jpeg

A microarray is a collection of gene probes which are attached to a solid surface. It consists of thousands of DNA probes arrayed on a single glass microscope slide or silicon chip. A gene probe is a specific length of single-stranded DNA, between 20 and 40 nucleotides long (or sometimes as large as 1000 nucleotides!) which is complementary to a known sequence of DNA form a particular gene.


A gene probe can measure the level of gene expression in a sample of DNA, and a microarray can screen a large number of genes at the same time. It is efficient and fast as it identifies genes which are expressed in certain individuals/breeds, while also showing those genes that are not being expressed as a comparison.


Microarrays can be used when scientists are trying to discern between genes that are desirable and genes that are not. For example, if some individuals are resistant to a particular disease, they may have a unique form of a gene that scientists would like to locate and analyse.

two.png
How are microarrays created?
Slide2.jpeg

The basic sequence for creating a microarray/locating a gene is as follows:


  1. A probe is a sequence of DNA which is made radioactive

  2. The target for the probe is double-stranded DNA containing the sequence being studies

  3. The target DNA is heat-treated to denature the strands and separate them

  4. The radioactive probe is introduced to find the gene


DNA microarray technology however has allowed for scientists to determine the expression of thousands of genes at one time. In the target cell, its mRNA is extracted, reverse transcribed into DNA (now called copy DNA or cDNA) and is labelled with a fluorescent marker. The fluorescently labelled DNA is then hybridised under stringent conditions to the probes on the slide. 


A scanner measures the fluorescence for each DNA probe on the slide, and from this information, scientists can work out the activity of the genes in the cell. The stronger the fluorescene, the more mRNA in the original sample and therefore the greater activity of each of the genes.

Topic Menu
DNA Tools, Techniques and Vocabulary
Polymerase Chain Reaction (PCR)
Gel Electrophoresis
Microarrays
DNA Sequencing

Want your ATAR notes to empower over 77,000 students per year?

Logo-New-Large.png

Join the Team.
Empower Education.

three.png

Sign Up for Free to Read More 

Get instant access to all content and subscribe to our weekly email list on study tips, opportunities and other free resources. 

It only takes a minute...

Slide3.jpeg
four.png
Slide4.jpeg
five.png
Slide5.jpeg
six.png
Slide6.jpeg
157-seven.png
Slide1.jpeg
156-eight.png
Slide8.jpeg