Gel electrophoresis lab
Thu, Oct 29, 2026 · Week 10 · Genetics of Disease (Medical Interventions)
Today's goal: Run or model gel electrophoresis and interpret band positions to compare DNA fragments.
What a finished product looks like
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
I recorded how far each band traveled from the well and used the size ladder to estimate the unknown bands.
Ranking, largest to smallest: Band 1 traveled the least (largest), then Band 2, then Band 3 traveled the farthest (smallest).
Size estimates: Unknown Band 2 lined up between the 1000 bp and 750 bp ladder bands, so I estimate about 850 bp. Unknown Band 3 lined up near the 500 bp ladder band, so I estimate about 500 bp.
Why smaller fragments travel farther: DNA is negatively charged, so the electric field pulls all fragments toward the positive end. The agarose acts as a sieve, and smaller fragments thread through the gel's pores more easily, so they move farther in the same time.
| Band | Migration distance | Size estimate |
|---|---|---|
| Ladder 1000 bp | 18 mm | 1000 bp (known) |
| Unknown Band 2 | 21 mm | ~850 bp |
| Ladder 500 bp | 30 mm | 500 bp (known) |
| Unknown Band 3 | 30 mm | ~500 bp |
Also due today: Submit your data table and interpretation to the course shell.
WebXam problem for today's skill
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.