What are good sources of DNA for analysis?

Cigarette butts and saliva are excellent sources of DNA for analysis due to the biological material they contain. Saliva is particularly rich in DNA because it can carry cells from the oral mucosa, which are often shed naturally in saliva. When examining a cigarette butt, the residue left by a user often includes saliva, which can provide a viable source of genetic material for forensic analysis.

In contrast, while blood and hair can contain DNA, the criterion presented in the correct answer highlights that there are multiple viable sources of DNA beyond these more traditional samples. Food wrappers and household items may contain trace DNA, but they are often less reliable as sources compared to biological specimens like saliva present on cigarette butts. Thus, the answer identifying cigarette butts and saliva emphasizes the practical aspects of DNA collection from everyday items that can provide valuable forensic evidence.