Final answer:
Lanes 3 and 4 on the PCR gel electrophoresis contain the PCR products from the same individual, as indicated by the distinct bands of DNA fragments amplified by PCR and visible on the agarose gel.
Step-by-step explanation:
The question pertains to identifying the lanes containing PCR products from the same individual in an agarose gel electrophoresis. In a typical PCR (Polymerase Chain Reaction) process, the genomic DNA is first denatured, and then primers anneal to the target sequences. With each cycle of PCR, the amount of the desired DNA segment increases exponentially. Lanes 3 and 4 contain amplified PCR products, as indicated by the bright bands visible after staining with ethidium bromide, which makes them fluoresce under ultraviolet light. Since both lanes contain the amplified product generated from the same DNA sample with different primer pairs, these two lanes have the PCR products from the same individual. It is confirmed by the presence of bands of distinct DNA fragments produced by PCR amplification in both lanes, which are visible on the agarose gel.