Nucleotide length terminology: What is the correct term for a short, synthetic nucleic acid molecule containing approximately 2–20 nucleotides used as a primer or probe?

Introduction / Context:
Short synthetic DNA or RNA strands are ubiquitous in molecular biology. They act as primers for PCR and sequencing, as probes for hybridization assays, and as building blocks for gene assembly and genome editing. The precise term for such short sequences is “oligonucleotide.”

Given Data / Assumptions:

• Length range of interest is roughly 2–20 nucleotides, though many oligos used in practice are 18–35 bases.
• Applications include PCR primers, qPCR probes, antisense oligos, and adapters.
• Chemical synthesis typically uses solid-phase phosphoramidite chemistry.

Concept / Approach:
Match each term to its definition. “Oligo” means few; thus an oligonucleotide is a short stretch. “Mononucleotide” is a single nucleotide unit. “Plasmid/vector” are much larger circular DNA constructs. “Polynucleotide” is a general term for long chains and does not specify short synthetic pieces used as primers or probes.

Step-by-Step Solution:

Verification / Alternative check:
Vendor catalogs and protocols refer to primers and probes as oligonucleotides, confirming common usage across applications.

Why Other Options Are Wrong:

• Plasmid/Vector: circular DNA carriers, thousands of base pairs.
• Mononucleotide: a single nucleotide, not an oligo.
• Polynucleotide: generic term for longer nucleic acid polymers.

Common Pitfalls:
Confusing the functional role (primer vs probe) with the class name; both are still oligonucleotides differentiated by use and labeling.

Final Answer:
Oligonucleotide