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Dna chips and microarrays
DNA microarrays contain thousands of DNA probes attached to a solid surface that allow for the simultaneous analysis of gene expression across many genes. The core principle is based on DNA hybridization, where fluorescently labeled cDNA or RNA samples are hybridized to complementary probes on the array. By detecting which probes light up after hybridization and washing, researchers can determine which genes are expressed or detect genetic variations in the sample. Microarrays have numerous applications, including gene expression analysis, disease diagnosis, drug discovery, and toxicology research. They provide a fast way to study thousands of genes but results require further validation and correlations do not necessarily indicate causation.
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Dna chips and microarrays
- 1. DNA chips and microarrays Biotechnology(FST 2163) Group no: 02 108018 108019 108078
- 2. Content o Introduction o Principle oTypes of microarray o Applications o Advantages and disadvantages o Summery o References
- 3. Introduction DNA chips andmicroarrays … o Made with thousands of nucleotide attached to a chip o Contains a particular cDNA sequence known as “probe” o Probes are deposited on a solid support, either positively charged nylon or glass slide o Probes occupy a particular “spot” on the chip
- 4.
- 5. Principle The core principlebehind microarrays is hybridization Samples are labeled using fluorescent dyes At least two samples are hybridized to chip Complementary nucleic acid sequences get pair via hydrogen bonds Washing off of non-specific bonding sequences
- 6. Principle cont… Fluorescently labeledtarget sequences that bind to a probe sequence generate a signal The signal depends on The hybridization conditions, ex: temperature washing after hybridization Total strength of the signal, depends upon the; amount of target sample
- 7. Principle cont… Microarrays userelative quantization in which the intensity of a spot is compared to the intensity of the same spot under a different condition Identity of the spot is known by its position
- 9. Scanning the arrays Laserscanners Excellent spatial resolution Good sensitivity, but can bleach fluorochromes Still rather slow CCD scanners Low resolution Sensitivity easily adjustable (exposure time) Faster and cheaper than lasers In all cases, raw data are images showing fluorescence on surface of chip
- 10. Types of Microarrays Thetypes of DNA microarrays most widely used today can be broadly divided into another two categories cDNA arrays Oligonucleotide arrays.
- 11. Produces by Affymetrix Anoligonucleotide array The most commonly used type of DNA microarray Each array contain hundreds of thousands of probe spots The Affymetrix Gene Chip
- 12. Each of thesespots contain millions of copies of an individual 25 base long DNA oligonucleotide
- 13. cDNA microarrays Each spotcorresponds entirely to a specific gene Measure complementary DNA , as it is more stable than mRNA at large sizes. mRNA from the original sample is reverse transcribed in a laboratory to create an equivalent number of the cDNA
- 14. These cDNAs are usuallymore than 500 bases long
- 15. Applications Gene expression analysis Notall the genes in the human genome are active at all times used to detect DNA , or detect RNA that may or may not be translated into proteins. The process of measuring gene expression via cDNA is called expression analysis
- 16. Thousand genes aresimultaneously assessed Study the effects of certain treatments, diseases, and developmental stages on gene expression. E.g.: identify genes expression changes due to pathogens or other organisms by comparing with uninfected cells or tissues
- 17. Help to investigateabout different diseases E.g.: Earlier cancers classified on the basis of the organs in which the tumors develop. Now, classify the types of cancer on the basis of the patterns of gene activity in the tumor cells. Help to produce very effective drugs Disease diagnosis
- 18. Extensive application inPharmacogenomics Comparative analysis of the genes Help the identification of the specific proteins produce by diseased cells Information used to synthesize drugs which combat with these proteins and reduce their effect. Drug Discovery
- 19. Toxicological Research A rapidplatform for the research of the impact of toxins on the cells and their passing on to the progeny. Important for Toxicogenomic studies
- 20. Small microarrays tocheck IDs of organisms in food and feed (like GMO) and mycoplasms in cell culture Mostly combining PCR and microarray technology Gene ID
- 21. Nutrigenomic research Study variationsin the genes related to the influence of diets. These variations, known as single nucleotide polymorphism
- 22. E.g.: Studies arefollowed to reveal, Effects of calorie restriction on gene expression Obesity and high-fat diets Genes responds to gluten and soy protein
- 23. Advantages and disadvantages Advantages Providesdata for thousands of genes One experiment instead of many Fast and easy to obtain results Huge step closer to discovering cures for diseases and cancer Different parts of DNA can be used to study gene expresion
- 24. Disadvantages Correlations in resultsdo not mean causation Very little knowledge is available about many genes Just because mRNA is "turned on" doesn't mean proteins are made The findings may lead to unethical medical procedures Scientists have no standardized way to share results
- 25.