Q.35 Which of the following is/are common to both prokaryotic and eukaryotic gene expression?
(A) Coupled transcription and translation (B) Post-translational modification
(C) Genetic code (D) Presence of the sequence TATA in the promoter
Prokaryotic and Eukaryotic Gene Expression: Common Features Explained
The correct answer to the question “Which of the following is/are common to both prokaryotic and eukaryotic gene expression?” is (C) Genetic code. This universal code ensures consistent translation of mRNA into proteins across all life forms. Understanding these differences and similarities aids in grasping molecular biology fundamentals.
Option Analysis
Coupled transcription and translation (A) occurs only in prokaryotes due to the absence of a nuclear membrane, allowing simultaneous processes in the cytoplasm. Eukaryotes separate these in nucleus and cytoplasm, preventing coupling.
Post-translational modification (B) is more extensive in eukaryotes, involving glycosylation and phosphorylation in organelles like the ER and Golgi. Prokaryotes perform simpler modifications like acetylation, but not to the eukaryotic extent.
Genetic code (C) remains identical in both, with 64 codons specifying 20 amino acids and stop signals, enabling universal protein synthesis.
TATA sequence in promoter (D) typifies eukaryotic core promoters for RNA polymerase II binding. Prokaryotes use -10 and -35 boxes instead.
Key Differences Table
| Feature | Prokaryotes | Eukaryotes |
|---|---|---|
| Transcription-Translation Coupling | Yes, coupled |
| | No, spatially separated | |
| Post-Translational Modifications | Basic (e.g., methylation) | Complex (e.g., glycosylation) |
| Genetic Code | Universal |
| | Universal |
| | |
| Promoter Sequence | -10/-35 boxes |
| | TATA box common |
| |
Why Genetic Code is Universal
The genetic code evolved early and conserved across domains due to its efficiency, with rare exceptions like mitochondria not altering its commonality in standard gene expression. This universality supports biotechnology applications like recombinant DNA.
