Polytene chromosomes in Drosophila serve as a classical model for cytogenetic studies. However, heterochromatic regions of chromosomes are typically under-replicated, hindering their analysis. Mutations in the Rif1 gene lead to additional replication of heterochromatic sequences, including satellite DNA, in salivary gland cells. Here, we investigated the impact of the Rif1 mutation on heterochromatin in polytene chromosomes formed in ovarian germ cells due to the otu gene mutation. By the analysis of otu11; Rif11 double mutants, we found that, in the presence of the Rif1 mutation, ovarian cells undergo additional polytenization of pericentromeric regions. This includes the formation of large chromatin blocks composed of satellite DNA. Thus, the effects of the Rif1 mutation are similar in salivary gland and germ cells. The otu11; Rif11 system opens new possibilities for studying factors associated with heterochromatin during oogenesis.
Keywords: Rif1; heterochromatin; polytene chromosomes; pseudonurse cells; satellite DNA; under-replication.
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