Title 23. GENE EXPRESSION.pdf ✅

PHARMD GURU Page 1 INTRODUCTION: Gene expression is the process by which genetic information encoded in DNA is transcribed into RNA and translated into functional proteins. While the fundamental principles of gene expression are conserved across all life forms, prokaryotic and eukaryotic systems exhibit significant differences in their regulatory mechanisms and cellular processes. EXPRESSION SYSTEMS IN PROKARYOTES AND EUKARYOTES: A. COMPARISON OF PROKARYOTIC AND EUKARYOTIC GENE EXPRESSION: FEATURE PROKARYOTIC GENE EXPRESSION EUKARYOTIC GENE EXPRESSION Complexity Simple and efficient More complex with multiple regulatory layers Transcription and Translation Occur simultaneously (coupled process) Occur separately due to compartmentalization mRNA Structure Polycistronic (can encode multiple proteins in one mRNA) Monocistronic (each mRNA typically encodes one protein) RNA Processing Minimal processing; mRNA is directly translated Extensive processing (5' capping, splicing, polyadenylation) Regulatory Elements Operons regulate gene clusters Enhancers, silencers, and chromatin modifications provide fine control B. DIFFERENCES IN TRANSCRIPTION PROCESSES: 1. PROKARYOTIC TRANSCRIPTION:  RNA polymerase binds directly to the promoter with the help of sigma factors.  Produces mRNA that is ready for translation immediately.  Transcription and translation occur simultaneously in the cytoplasm. 2. EUKARYOTIC TRANSCRIPTION:  RNA polymerase II requires multiple transcription factors to initiate transcription. GENE EXPRESSION