This project performs data preprocessing on DNA methylation microarray data collected using the Illumina MethylationEPIC BeadChip interrogateíng over 850,000 methylation sites on 45 pairs of monozygotic twins discordant for multiple sclerosis (MS). The task of the project includes loading raw methylation data, converting intensity signals to methylation measurements, quality control, normalization, detection of batch effects, transformation of data for statistical analysis. At the last step, the project will perform a genome-wide association analysis of MS to identify genomic sites and regions differentially methylated for MS. The project will be done using the free R package minfi (https://bioconductor.org/packages/release/bioc/vignettes/minfi/inst/doc/minfi.html) for both data preprocessing and data analysis. The project fits an ISA project with 10 ECTS.