Isolation of Drosophila clones encoding maternally restricted RNAs

We have isolated molecular clones encoding RNAs which appear to be transcribed predominantly or exclusively during oogenesis in Drosophila melanogaster. These clones were isolated by virtue of their homology to polyadenylated RNAs present in very early embryos and absent from older embryos. An analysis of the developmental expression of three cloned genes is presented. The genomic position of one of these clones coincides closely with the position of the maternal effect lethal gene swallow, providing strong evidence that we have cloned this locus.