In a control experiment, a plasmid containing a HindIII recognition sequence within a kanamycin resistance gene is cut with HindIII, re-ligated, and used to transform \(E .\) coli K 12 cells. Kanamycin-resistant colonies are selected, and plasmid DNA from these colonies is subjected to electrophoresis. Most of the colonies contain plasmids that produce single bands that migrate at the same rate as the original intact plasmid. A few colonies, however, produce two bands, one of original size and one that migrates much less far down the gel. Diagram the origin of this slow band as a product of ligation.

In this control experiment, a plasmid containing a HindIII recognition sequence within a kanamycin resistance gene is cut with HindIII, which cleaves the DNA at the recognition site. The DNA is then re-ligated and used to transform \(E. coli\) K 12 cells. The kanamycin-resistant colonies are selected, and plasmid DNA from these colonies is subjected to electrophoresis.

Most of the colonies contain plasmids that produce single bands that migrate at the same rate as the original intact plasmid. On the other hand, a few colonies produce two bands, one of original size and one that migrates much less further down the gel (slow-migrating band).

The slow-migrating band could have emerged due to incorrect re-ligation of the cleaved plasmid DNA during the control experiment. This could result in the plasmid forming a larger molecule containing extra or incorrectly re-ligated DNA sequences. Larger molecules migrate slower on the gel compared to smaller molecules.

To illustrate the origin of the slow band, we can draw the following diagram: 1. Start with the original plasmid containing a HindIII recognition site within a kanamycin resistance gene. (A circle with the HindIII site and kanamycin resistance gene marked) 2. Cut the plasmid with HindIII, resulting in a linear DNA molecule with two overhangs where it was cut. (A straight line with the two ends marked as HindIII overhangs, and the kanamycin resistance gene portion separated) 3. During re-ligation, instead of correctly joining the two ends back together, the DNA molecule may form a larger loop or concatemer with other plasmid molecules or extra DNA sequences. (An enlarged circle with the HindIII site and kanamycin resistance gene marked, plus any extra or misaligned DNA sequences) 4. On gel electrophoresis, this larger looped or concatenated molecule would migrate slower on the gel, resulting in the observed slow-migrating band. (Electrophoresis gel image showing two bands: one for the original intact plasmid and the other for the larger ligation product)