What can be a common reason for low yield in DNA extraction?

Correct answer: Incomplete cell lysis

The governing concept is recovery of DNA from the starting biological material. Efficient cell lysis is essential because intact cells or nuclei retain DNA, preventing it from entering the extraction solution. If the lysis buffer is unsuitable, the incubation is too short, the sample is not mixed adequately, or the material is difficult to disrupt, only part of the available DNA is released. The final measured yield is then low. Option A is correct. Good precipitation and correct elution generally improve recovery, while a perfect sample is not a cause of low yield. Losses can also occur later, but incomplete lysis is a common early cause.