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Period: to
Before bioinformatics
In this period the theory of transmission of heredity by Gregor Mendel, which later became known as the laws of genetics, and the discovery of the components of DNA by scientists such as Kossel and Levene. -
Proposed double helix model
The double helix model is published in the journal Nature, under the names of Watson and Crick, but the work of Rosalin Frankling, who took the "51st photograph" and discovered the double helix shape of DNA, is left out. This made it possible to understand at the molecular level the organisation, sequencing, and heritability of genes. -
Period: to
Bioinformatics era
At this time, gene sequencing software was developed that was able to sequence large quantities of complete genomes in a short time, which led to a great leap forward in genomic sciences. -
Atlas of protein sequence
The double helix model is published in the journal Nature, under the names of Watson and Crick, but the work of Rosalin Frankling, who took the "51st photograph" and discovered the double helix shape of DNA, is left out. This made it possible to understand at the molecular level the organisation, sequencing, and heritability of genes. -
Grunstein and Hogness colony hybridisation method
In this method, which is the first predecessor of microarrays, E. coli plasmids were cloned for the first time to obtain DNA spots, but these were random and disordered. These samples, obtained to identify clones with complementary DNA sequences, made it possible to study the genome of a population of bacteria together, and the transmission of a desired gene. -
cDNA studies
Complementary DNA molecules have a strand that is complementary to the messenger RNA sequence, and can be used for gene cloning or hybridisation, so their study could be applied in the development of mRNA arrays, as there are enough gene samples to be studied. -
Human Genome Project
The human genome project began in 1990 with the task of sequencing the complete human genome. This project was a breakthrough, which in its 10 years of duration, until 2001, promoted the development of new techniques such as gene hybridisation, the creation of reference sets of cDNA and new technologies for gene sequencing. -
Affymetrix Foundation
Affimetrix is a state-owned bioinformatics company specialising in the creation and design of microarrays, biotechnology scanners and microchips. It was founded by Stephen Fodor and has been at the forefront of microarray design since its inception. -
Microarray in situ
The in situ microarrays designed by Fodor and Affymetrix are characterised by the use of directed light and a lipid layer on the matrix, where the sample is placed. This allows laser analysis to be carried out with just a few reagents. But each lipid layer must be specific for each experiment, so it is expensive. It was used in the detection of mutations in reverse transcriptase genes, and it is also used for genotyping. -
Spotted microarrays
This type of microarray, designed by Derisi, was high-density and used glass, as well as using fluorescent markers instead of radioactive ones, and a robotic detector was designed that could detect several carriers. This new method allowed two different samples to be marked and joined together in a single sample holder, avoiding false differences in colour and making the process easier to replicate.
It is used in gene expression analysis. -
Self assembled microarrays
In this method, polystyrene beads are used to synthesise DNA, then placed at the end of a fibre-optic array, where there are small collapses where only one bead remains, different fluorescently labelled beads from two different DNA syntheses are mixed together, resulting in self-assembly of the beads on the microarray. -
New Horizon
Hoguen Kim writes in a 2004 article how the use of microarrays is a useful tool in the accurate and objective diagnosis of tumours by detecting changes in gene expression. Despite their limitations, these new diagnostic methods look promising. -
Limitations
Microarrays were a great tool in the 1990s but as Bumgarner points out in a 2013 article, their range of action is small as they need to have a sample of the mutation you want to find to perform the practice and cannot find new ones on their own, like modern sequencers, and they confuse different genes as to whether they belong to the same gene family.
Microarrays are being replaced, but they have found a new niche in cancer diagnosis. -
A Microrray metadata
The research group aims to map post-tumour damage transcription mutations in cancer with microarray samples: 200 from healthy tissue, 130 from adenoma and 340 from CRC (colon cancer cells). Disparate results are eliminated by a systemic review to arrive at a consensus, which serves as a model for the study of early cancer formation and clinical diagnosis. In addition, this model is easy to adapt to other types of cancer. -
References
Bumgarner, R. (2013). DNA microarrays: Types, Applications and their future. <i>Current Protocols in Molecular Biology / Edited by Frederick M. Ausubel ... [et Al.] https://doi.org/10.1002/0471142727.MB2201S101</div>
Kim, H. (2004). Role of Microarray in Cancer Diagnosis. <i>Cancer Research and Treatment : Official Journal of Korean Cancer Association https://doi.org/10.4143/CRT.2004.36.1.1</div> -
Reference
Rohr, M., Beardsley, J., Nakkina, S. P., Zhu, X., Aljabban, J., Hadley, D., & Altomare, D. (2021). A merged microarray meta-dataset for transcriptionally profiling colorectal neoplasm formation and progression. <i>Scientific Data 2021
https://doi.org/10.1038/s41597-021-00998-5</div>