Reduction of ribosomal RNA synthesis and ribosomal RNA genes in a mutant of Xenopus laevis which organizes only a partial nucleolus. I. Ribosomal RNA synthesis in embryos of different nucleolar types.

摘要: Abstract During early embryonic development, a newly described mutant of Xenopus laevis which organizes only partial nucleolus synthesizes ribosomal RNA at 25 to 40% the rate attained in wild-type embryos. A deletion one nucleolar organizer ( lethal or p l nu ) and total other o are combined this /o ), resulting condition permits normal development swimming tadpole stage, when dies. The is constructed by crossing an animal heterozygous for mutation (+/ with carrying ). progeny, distinguishable cytologically their condition, are: +/+ (wild-type), +/ , . first three types all develop normally synthesize rRNA same rate. At every stage synthesis embryos reduced. This reduction not caused error conversion precursor mature rRNA. therefore exemplifies class mutants deletions related alterations synthesis. Such should facilitate analysis control transcription rRNA, while comparison made different sizes might help reveal any heterogeneity that may exist