We have identified genes in a family of hundreds of repeated elements (junk DNA) scattered in the human genome. They code for DNA-binding proteins with double homeodomains (DUX). The DUX4 gene is repeated as a tandem in locus D4Z4 located on chromosome 4 and associated with a hereditary muscular degeneration disorder: facioscapulohumeral dystrophy (FSHD). The DUX4 protein is toxic and we think that its expression causes FSHD. This protein is a kind of mad professor which disturbs the activity of dozens of genes. Its neighbouring DUX 4c gene produces a nontoxic protein in muscles, which is more abundant in diseased people. We study the expression and the function of these proteins.