Structural organization and processing of the genetic transcript in the cellular slime mold XXXX .

@entity4328 @entity2036
The organization of the genome and the synthesis and processing of heterogeneous nuclear RNA (HNRNA) in the cellular slime mold Dictysotelium discoideum have been analyzed. Approximately 60-70% of the genome of @entity4328 consists of interspersed reiterated and single-copy sequences. The interspersed reiterated sequences have an average length of 250-400 @entity2036 . Approximately 50% of the reiterated DNA sequences consist of long noninterspersed sequences. The results of analyses of ynRNA synthesis and processing have been incorporated into a model. According to the model the primary genetic transcript of @entity4328 is synthesized as a molecule that is 25% larger than mRNA. The bulk of the hnRNA is synthesized from a unit consisting of a short reiterated DNA sequence transcript at the 5' end of the molecule and a single-copy sequence of approximately 1,200 @entity2036 in length. In the processing of the mRNA precursor, there appears to be a loss of the majority of the repetitive sequence at the 5' end. The genome contains interspersed sequences of poly (dT)25. These sequences, which appear to be at the 3' terminus of the transcription unit, are transcribed directly into the heterogenous nuclear RNA and are contained within the messenger RNA. During the processing of the heterogeneous nuclear RNA, a poly (A) sequence of approximately 125 @entity2036 in length is added posttranscriptionally to the 3' end of the molecule.
