Crime-scene work often involves obtaining a DNA sample from a drop of blood to help identify persons who may have been involved. Frequently, the size of the DNA sample is extremely small, too small for easy analysis. Which of the following laboratory procedures could criminologists use to amplify the amount of DNA present? Cloning and gel electrophoresis Cloning and polymerase chain reaction (PCR) DNA splicing and polymerase chain reaction (PCR) Vector amplification and DNA splicing