What is a major component of the structure of a typical virus?

The correct answer highlights that a core of DNA or RNA is a fundamental aspect of a virus's structure. Viruses are unique entities that consist predominantly of genetic material encapsulated within a protein coat, known as a capsid. This genetic material can either be composed of DNA or RNA, which contains the instructions necessary for the virus to replicate and propagate within a host organism.

Unlike cellular organisms, viruses lack the cellular structures such as membranes or walls, which means they do not have a membrane bilayer or cell wall as seen in bacteria or plant cells. Additionally, chloroplasts are specialized organelles found in plant cells and are not part of any virus structure. The presence of nucleic acids allows viruses to hijack the cellular machinery of their host to produce new viral particles, which is central to their lifecycle. Thus, identifying a core of DNA or RNA as a major component accurately reflects one of the defining characteristics of viruses.