1. a) Each band in a DNA electrophoresis gel is made up of many molecules of one DNA fragment size.
b) Gel electrophoresis can tell you the relative size of a particular DNA fragment, not its sequence.
c) You can see DNA on a gel because it is stained with a fluorescent dye (like ethidium bromide or SYBR Safe), not because DNA is naturally fluorescent.
d) DNA moves through a gel because it is negatively charged and is attracted to the positive electrode.
e) The speed at which DNA moves through a gel is inversely related to its size (smaller fragments move faster).
f) An electrophoresis gel used for DNA is usually made from agarose, which is a protein extracted from seaweed.
g) When visualizing your gel, you can tell the size of the DNA fragments by comparing their position to the ladder bands, not by seeing how wide each band is.
h) A gel is placed in a liquid called running buffer because it conducts electricity and maintains a stable pH, not because it is an insulator.
2. Fragment F is the largest. It traveled the shortest distance from the well, indicating it is the largest fragment. In gel electrophoresis, larger fragments move more slowly through the gel matrix than smaller ones.
3. Fragments B and D are the same size. They migrated to the same position (same distance from the well) in different lanes, indicating they have identical molecular weights/fragment lengths.
4. Lane 5 contains a DNA fragment that is about 700 base pairs. The fragment in lane 5 aligns with the position between the 600 bp and 800 bp markers on the ladder.
5. Fragment E is about the same size as the length of fragment A and fragment F added together. Fragment A is approximately 300 bp and fragment F is approximately 400 bp; their sum is 700 bp, which matches the size of fragment E.
Parent Tip: Review the logic above to help your child master the concept of gel electrophoresis worksheets.
