What is a plasmid?

A plasmid is best defined as a small, circular DNA molecule found in bacteria, often used for gene cloning. Plasmids are separate from the chromosomal DNA and can replicate independently of the chromosomal DNA, which allows them to be used as vectors in genetic engineering. They can carry genes that may benefit the survival of bacteria, such as antibiotic resistance genes. In laboratory settings, scientists often manipulate plasmids to insert specific genes for various applications, including the production of proteins and the study of gene function.

While other options mention important biological components, they do not accurately describe the characteristics and functions of plasmids in the context of gene cloning and molecular biology. For instance, linear DNA molecules that form chromosomes refer to eukaryotic DNA structure, while RNA molecules primarily transport genetic information for protein synthesis, and integral proteins are components of cell membranes, unrelated to plasmid function.