Which feature is shared by both DNA replication and transcription in cells, considering polarity and chemistry of chain elongation?

Introduction / Context:
DNA replication and transcription are distinct processes performed by different enzymes, yet they share core polymer chemistry. This question checks understanding of the universal polarity of nucleic acid synthesis.

Given Data / Assumptions:

• Replication uses DNA polymerases and deoxynucleotides.
• Transcription uses RNA polymerases and ribonucleotides.
• Both extend nucleic acid chains by phosphodiester bond formation.

Concept / Approach:
Both polymerases add nucleotides to the 3'-OH of the growing strand, proceeding 5'→3'. However, replication incorporates deoxynucleotides, whereas transcription incorporates ribonucleotides, and the enzymes are unrelated in subunit composition and specificity.

Step-by-Step Solution:
1) Identify shared property: chain growth polarity (5'→3').2) Exclude deoxynucleotide incorporation: true for replication, not transcription.3) Exclude shared enzyme use: DNA vs RNA polymerase are different.4) Therefore, the commonality is 5'→3' synthesis.

Verification / Alternative check:
Mechanistically, both form a bond between the 3'-OH of the primer strand and the alpha phosphate of an incoming NTP/dNTP, releasing pyrophosphate—consistent with 5'→3' growth.

Why Other Options Are Wrong:
Deoxynucleotide incorporation: specific to replication.Same enzyme: false; different polymerases and co-factors.None of the above: incorrect because polarity is shared.

Common Pitfalls:
Assuming symmetry between processes or overlooking ribose vs deoxyribose differences.

Final Answer:
Synthesis in the 5'-3' direction