In recombinant DNA technology, what is meant by the term vector?

Introduction / Context:
This question checks your understanding of a core concept in genetic engineering and biotechnology: the vector. Vectors are essential tools in recombinant DNA technology, allowing scientists to introduce foreign DNA into host cells for cloning, expression, or analysis.

Given Data / Assumptions:

• We are dealing with recombinant DNA methods, such as cloning genes in bacteria.
• The term vector is being used in a molecular biology context, not in a physics or epidemiology context.
• The options describe sticky ends, plasmids, DNA probes, and restriction enzymes.
• We need to identify which description matches the role of a vector.

Concept / Approach:
In recombinant DNA technology, a vector is a DNA molecule that can carry foreign DNA into a host cell and replicate there. Common vectors include plasmids, bacteriophages, and artificial chromosomes. Vectors must have features such as an origin of replication, selectable markers, and cloning sites. Sticky ends, DNA probes, and restriction enzymes are important tools but are not vectors themselves. By recalling the typical example of a plasmid vector, we can select the correct option.

Step-by-Step Solution:
Step 1: Recall that plasmids are small, circular DNA molecules found in bacteria that can replicate independently of chromosomal DNA.Step 2: In recombinant DNA experiments, plasmids are engineered to carry foreign DNA fragments, creating recombinant plasmids.Step 3: These plasmid vectors are introduced into host cells, where they replicate and express the inserted gene.Step 4: The term vector therefore refers to this carrier molecule, usually a plasmid, phage, or similar DNA, that transfers genetic material into cells.Step 5: Thus, the correct option is the one that describes a plasmid or similar carrier used to transfer DNA into a living cell.

Verification / Alternative check:
Many introductory diagrams of genetic engineering show a plasmid being cut open by a restriction enzyme, receiving a foreign DNA fragment, and then being reintroduced into a bacterium. The plasmid in this picture is always labeled as the vector. Sources repeatedly emphasize vectors as carriers or vehicles for genes, which confirms the selected option.

Why Other Options Are Wrong:
Sticky end of a DNA fragment: Sticky ends are short single stranded overhangs created by restriction enzymes, useful for joining DNA fragments, but they are not carriers of DNA into cells.
Short DNA probe: A DNA probe is a labeled DNA sequence used to detect complementary sequences, but it does not serve as the main vehicle for delivering genes into host cells.
Restriction enzyme: These enzymes cut DNA at specific sequences, enabling cloning, but they are proteins, not DNA molecules, and are not vectors.

Common Pitfalls:
Students may mix up tools used in recombinant DNA experiments and assume that any important component, such as a restriction enzyme or probe, might be called a vector. It is important to remember that a vector must be a replicating DNA molecule that carries foreign DNA into a host. Keeping this carrier concept in mind avoids confusion.

Final Answer:
In recombinant DNA technology, a vector is A plasmid or similar carrier used to transfer DNA into a living cell.