RESUMO
Stocks of D. melanogaster X chromosomes carrying terminal deletions (RT chromosomes) have been maintained for several years. Some of the chromosomes are slowly losing DNA from the broken ends (as expected if replication is incomplete) and show no telomere-associated DNA added to the receding ends. Two stocks carry chromosomes that have become "healed" and are no longer losing DNA. In both stocks the broken chromosome end has acquired a segment of HeT DNA, a family of complex repeats found only at telomeres and in pericentric heterochromatin. Although the HeT family is complex, the HeT sequence joined to the broken chromosome end is the same in both stocks. In contrast, the two chromosomes are broken in different places and have no detectable sequence similarity at the junction with the new DNA. Sequence analysis suggests that the new telomere sequences have been added by a specific mechanism that does not involve homologous recombination.
Assuntos
Aberrações Cromossômicas/genética , Reparo do DNA/genética , Drosophila melanogaster/genética , Cromossomo X/ultraestrutura , Animais , Sequência de Bases , Deleção Cromossômica , Clonagem Molecular , Feminino , Masculino , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Mapeamento por Restrição , Homologia de Sequência do Ácido Nucleico , Cromossomo X/fisiologiaRESUMO
Colonization with group B streptococci of the genital tract was studied in 1 115 women during the last trimester of pregnancy. 76 or 6.82% were found to harbour this bacterium. The incidence of contamination was significantly higher among Belgian women than among parturients of Mediterranean origin (p less than 0.001). It was also more frequent in primigravidae (p less than 0.05) and in the poorer (0.10 less than p greater than 0.05). At the time of admission in the delivery room, it was noticed that rupture of the amniotic membranes for more than 24 hours was more often associated with group B streptococcal carriage by the mother (p less than 0.001). 29 out of 68 (42.6%) infants born to group B streptococci positive mothers were colonized at birth. 67 of them were submitted to a controlled trial of immediate versus delayed penicillin therapy. 44.8% and 42.1% of the neonates were contaminated at birth in each group of treatment respectively. No instance of group B streptococcal infection developed in either group. This suggests that immediate therapy with penicillin of infants of group B streptococci positive mothers has no definite advantage upon delayed treatment.
