Mycobacterium bovis, shares 99.9% of genomic identity with M. tuberculosis, M. africanum and M. microti. Within this 0.1 % of difference, there are two genetic regions characteristics of M. bovis that are deleted in M. tuberculo­sis H37Rv: RvD1 and RvD2. According to bioinformatic analysis, these regions contain Open Reading Frames (ORFs). With the purpose of determining if the RvD1 region transcribes the ORFs predicted by bioinformatics (ORF1, ORF2 and Rv2024); total RNA was extracted from a

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... lture of M. bovis BCG Pasteur, at different time points along the growth curve. The RNA samples were analyzed by Real Time Reverse Transcription - Poly-merase Chain Reaction (RTq-PCR). The findings show that ORF1, ORF2 and Rv2024, were transcribed consti-tutively, something that has not been reported previously. These results are a first step in order to determine the function of M. bovis RvD1 region, its possible role in pathogenesis and its interaction with both cattle and humans. Key words: Mycobacterium bovis, BCG, RNA, Real Time, RT-PCR, RvD1