After running your gel, you receive the image below.  This technique separates the DNA fragments based on size . Larger DNA fragments are found near the top of the gel because it takes them longer to move through the pores of the gel. Shorter DNA fragments are found near the bottom of the gel because they move more quickly through the pores of the gel when compared to larger DNA fragments. Refer to the image above to answer this question. A DNA ladder consists of known sizes of fragments of DNA, and this can be referenced to estimate the sizes of other fragments. If the gene you isolated is ~450 base pairs (bp) in size, then Band A is the band that represents the DNA fragment that contains the gene.