Where sensitive techniques such as PCR are concerned, components of the contaminating DNA are likely to be amplified, thus leading to false positive results.

On the other hand, nucleic acids themselves, in particular DNA as the more stable molecule, present a source of contamination. This is especially true for RNA, as it is inherently unstable, and RNases are practically ubiquitous. Nucleic acids and proteins are compromised primarily by molecules nucleic acids, for example, are threatened by nucleases – enzymes which degrade nucleic acids.

Bacterial cultures, too, can be overgrown with other strains or molds. Critical contaminations arising during cell culture are dominated by the faster growing microorganisms (such as bacteria or molds) and infecting mycoplasma, but substances such as endotoxins that are detrimental to cells also play a role. Sample material in biological laboratories mainly comprises cells, microorganisms, nucleic acids and proteins that are either processed or analyzed directly.