A gene that does not contain introns has an Eco RI site just down stream of the translational termination codon in the 3' untranslated region. The size of the gene is 4 Kbp. The length of 3' UTR is 2 Kbp, the 5' UTR is 1 Kbp and that the open reading frame is 1kbp. Upon probing a southern blot of an Eco RI digested genomic DNA with the radioactively labelled fragment containing only the open reading frame, the size of the band detected by hybridization would be