Satellite DNAs are highly repeated sequences of unknown function. The satellite DNA from the meal worm beetle is remarkable since it represents over 50% of this insects genome. In this exercise, students first isolate DNA from beetle larvae by a simple and safe procedure. They then digest the DNA with EcoR1 and examine the satellite DNA following electrophoresis as shown on the gel pictured below. Suffient materials are provided so that the experiment can be carried out twice by eight groups of students. The exercise can be completed in two, two to three hour laboratory sessions and requires ethyl alcohol, a microcentrifuge and Electrophoresis Package 3/4.

In this exercise, DNA isolated from beetle larvae was digested for 0, 5, and 20 minutes (lanes 1-3, 5-7) with EcoR1 prior to this electrophoretic analysis. Note the progressive breakdown of the DNA satellite to the satellite monomer which is 142 base-pairs in length. DNA size markers are shown in lanes four and eight.