3.  The human genome contains approximately 21000 genes.  At any given moment, each of our cells has some combination of these genes turned on & others are turned off. how do scientists figure out which are on & which are off ?  Scientists can answer this question for any cell sample (or) tissue by gene expression profiling, using a technology called “microarray”.  “Microarray involves breaking open a cell, isolating its genetic contents, identifying all the genes that are turned on in that particular cell,& generating a list of these genes”.

5.  Scientists know that a mutation (or) alternation- in a particular gene’s DNA may contribution to a certain diseases.  However, it can be very difficult to develop a test to detect these mutations, because most large genes have many regions where mutations can occur.  DNA Microarray is a tool used to determine whether the DNA from a particular individual contains a mutation in genes.  “DNA Microarray is the devices for checking a sample of DNA simultaneously for the presence of many sequences (or) interactions among thousands of genes simultaneously”. DNA MICROARRAY

10. PROCESS OF DNA MICROARRAY

11. 1.COLLECTION OF TISSUES

12. 2. ISOLATION OF RNA

13. 3. ISOLATION OF mRNA

15. 4. MAKE LABELLED DNA COPY

16. 5.FORMATION OF cDNA

17. 6.APPLY TO MICROARRAY

18. 7. Scan the microarray