Question

Bacterial cells couple the process of transcription and translation. In eukaryotic cells, the process of transcription and translation are uncoupled or occur separately. Provide explanations as to why bacterial cells can couple the process of transcription and translation while in eukaryotic cells, the process is separated.

Answer 1

In prokaryotic cells, the translation of mRNA into protein can begin even before transcription is complete, as mRNA is produced in the cytoplasm. The codons of an mRNA are available to ribosomes before the entire mRNA molecule is even made.
The spatial and temporal separation of transcription and translation enables eukaryotes to regulate gene expression in a better way. This is contributing to the diversity of eukaryotic form and function by means of their protein diversity. In prokaryotes, the primary transcript serves as mRNA and is used immediately for protein synthesis. When an RNA transcript is first made in a eukaryotic cell, it is considered a pre-mRNA and must be processed into a mRNA.

In eukaryotes, mRNA precursors are processed and spliced in the nucleus before being transported to the cytosol. Primary transcripts acquire a cap at their 5′ ends and a poly(A) tail at their 3′ ends and are spliced. Introns are precisely excised from primary transcripts, and exons are joined to form mature mRNAs during splicing. Some mRNAs are only a tenth the size of their precursors.

Splicing allows for a process called alternative splicing, in which more than one mRNA can be made from the same gene. In alternative splicing, one pre-mRNA may be spliced in different ways. It plays a critical role in the regulation of gene expression and protein diversity in a variety of eukaryotes.