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Agarose gel

This is an example of a gel to detect DNA.  Each column has a different sample.  The purpose of a gel is to separate pieces of DNA by size, the smaller sizes are closer to the bottom of the gel.  The DNA is made visible by the presence of a fluorescent DNA dye in the gel. 

The second to last column (or lane) is standard sizes of DNA fragments to compare with the samples in the other lanes.

This gel shows that the first three lanes each have a DNA fragment (obtained by PCR) that is approximately 79 base pairs in length.

The last lane shows a sample of genomic DNA, which looks smeary because the very long DNA is broken in random places.  The streaks of white are from the camera reflection.

These PCR reactions were obtained from corn DNA by amplifying a normal corn gene, designated hmgA.