Why is it important to correctly identify the pellet and supernatant?

Correct answer: To avoid losing DNA

Centrifugation separates a mixture into a pellet at the bottom and a supernatant above it, but the location of DNA depends on the particular isolation protocol and step. DNA may be precipitated into the pellet, remain dissolved in the supernatant, or be present in a fraction that must be retained for a later precipitation or purification step. Correctly identifying the two layers prevents accidental disposal of the fraction containing the target nucleic acid. Option A is correct because discarding the wrong layer can cause substantial or complete DNA loss. The other choices concern sensory observations that have no role in deciding which fraction should be kept.