RESUMO
Non-mobile retrotransposons mdg1het and aurora localized in Drosophila melanogaster heterochromatin were studied. A novel retrotransposon aurora comprising 324 bp LTRs was revealed as a 5 kb insertion causing 5 bp duplication of integration site in the heterochromatic Stellate gene. All the aurora copies are immobilized in D. melanogaster heterochromatin and adjoining chromosome regions 40, 41C and 80BC. Mobile aurora copies were revealed in D. simulans euchromatin by in situ hybridization technique. A comparison of 2.5 kb sequence of immobile mdg1het (including a half of ORF2 and 3'-LTR) with the correspondent sequence of transposable mdg1 copy [9] allowed to conclude that evolution of mdg1 subfamilies occurred under the selective pressure for the ability to transpose. The time period passed since the aurora and mdg1 copies integrated in heterochromatin was roughly estimated via divergence extent between the left and right LTR; for aurora copy it is 0-0.15 Myr, and for mdg1het copies it is 0-0.7 Myr.
Assuntos
Elementos de DNA Transponíveis/genética , Drosophila melanogaster/genética , Heterocromatina/fisiologia , Animais , Sequência de Bases , Engenharia Genética , Hibridização In Situ , Dados de Sequência MolecularRESUMO
A method of generating unidirectional deletions from the cleavage site of any endonuclease by means of exonuclease Bal31 is developed. DNA sequence to be prevented from Bal31 hydrolysis is protected by a special "protector" element TH (Trojan Horse) inserted upstream of the sequence.