Biotechnology
PCR needs template DNA, primers flanking a target, nucleotides, and a heat-stable polymerase; repeated denaturation, annealing, and extension amplify the target. DNA generally moves toward the positive electrode in a gel because its phosphate backbone is negatively charged. Shorter fragments usually travel farther through a standard agarose gel. Restriction enzymes cut particular sequences, ligase joins DNA, and plasmids can carry engineered genes. Always distinguish DNA presence, RNA abundance, and protein function: they are different measurements.
A 300-base-pair PCR band confirms a fragment of the expected size, not automatically a correct sequence or a functional protein. A no-template reaction helps detect contamination.
A bright gel band is not proof that a gene is highly expressed. PCR of genomic DNA and measurement of gene expression answer different questions.