In a eukaryotic cell transcription results in a molecule of pre-mRNA that is modified to produce mRNA. in a prokaryotic cell transcription produces mRNA directly

explain this difference

Prokaryotes do not have introns, eukaryotes have introns

Explanation:

Prokaryotes do not have introns, eukaryotes do. Introns are regions of DNA that are transcribed but not part of the final protein. They interrupt exons, which are the coding parts of the gene. These are only present in eukaryotes.

Introns need to be removed before the mRNA can be translated into the protein sequence. This occurs by a process called splicing. The splicing machinery binds the junction between introns and exons and excises the intron. The exons are then fused together to create the mRNA.

Other processing steps occur to the eukaryotic pre mRNA to prevent it from being degraded in the cell. This includes adding a cap to the 5' end of the protein, and adding a poly A tail to the 3' end. One these steps are complete, the eukaryotic mRNA is complete.

The prokaryotic mRNA undergoes transcription and translation simultaneously because it doesn't require these processing steps.