In 11 generations of pigs transgenic on mMT1/RhGH gene and their untransgenic analogs the authors evaluated the degree of cytogenetic variability on the frequency of chromosomal aberrations and the amount of nucleolar organizers. It was revealed that the part of aberrant cells in transgenic animals is reduced with an increasing of generation number. The reliable exceeding of amount of active nucleolar organizers was marked in comparison with control in transgenic animals in all examined generations.

Key words: aberrations, transgenic pigs, chromosomes, nucleolus organizer.