Complex sentence: For visualization purposes, the DNA fragment is usually labeled with a radioactive, fluorescent or biotin label, as standard ethidium bromide staining lacks the sensitivity to detect the relatively small amounts of DNA used in these experiments.
Split into simpler sentences: For visualization purposes, the nucleic acid fragment is usually labeled with a radioactive, fluorescent or biotin label. Standard ethidium bromide staining is less sensitive than these methods and can lack the sensitivity to detect the nucleic acid if small amounts are used in these experiments.