Final answer:
A computer virus is a self-replicating code that spreads by attaching itself to a host program and utilizing the host's resources to replicate.
Step-by-step explanation:
A computer virus is a piece of self-replicating code embedded within another program called the host. Viruses are not cells; they consist of a strand of genetic material within a protective protein coat called a capsid, and they can replicate only by infecting a host cell.
They use the host cell's ATP, ribosomes, enzymes, and other cellular components to replicate. This biological process is analogous to how a computer virus operates, hijacking a computer system's resources to copy itself and spread.
Replication of DNA fragments in biotechnology, such as with the use of plasmids as vectors in cloning, also involves incorporating foreign DNA into a host cell's genome. Plasmids replicate independently of chromosomal DNA and are reintroduced into bacterial hosts so that the foreign DNA can be replicated and studied.