![Marker-assisted selection in apples on an agarose gel.](http://static.sciencelearn.org.nz/images/images/000/000/946/full/marker_assisted_selection_in_apples_oversize20160310-1390-gss3bu.jpg?1674165197)
DNA markers can be used to determine whether a seedling carries an allele of interest. Here, the marker for the red-flesh allele is detected as an additional DNA band on an agarose gel. Breeders use information like this to decide which seedlings to grow and which to discard.