Hello

I intend to use Infinium/Illumina **450K human methylation** array data in cancer studies. I need to understand if **data for normal sample** is required? I am planning to download data from tcga (where normal data isn't available).

Also another basic doubt is "if the **normal and tumor sample is mixed** when loading onto the slide"?
Tumor and normal are not hybridized on the same slide. Whether or not you need normal is not a question of bioinformatics, but of biology. In other words, you need to define what questions you are going to address. If those questions include comparison to normals, you will need normals.