SDS-PAGE gel results
Fri, Dec 11, 2026 · Week 16 · Genetics of Disease (Medical Interventions)
Today's goal: Read an SDS-PAGE gel to judge the size and purity of your isolated protein.
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.
How I read the gel: the marker (ladder) lane has bands of known molecular weights, so I use it as a ruler. Smaller proteins migrate farther down the gel, so I compare how far my band traveled to the marker to estimate size.
Reading:
- My target band lines up near the 27 kDa marker band, so I estimate the protein is about 27 kDa.
- Fraction 4 shows one strong band with almost no extra bands; fraction 2 shows several bands. So fraction 4 is the most pure.
QC statement: the purification met the purity goal, because the target fraction shows one dominant band at the expected size with very few contaminant bands, which is what a pure sample looks like.
| Lane | Bands seen | Estimated size | Note |
|---|---|---|---|
| Marker | Ladder of known sizes | reference | used as ruler |
| Fraction 2 | Several bands | mixed | impure, many contaminants |
| Fraction 4 | One dominant band | about 27 kDa | most pure, meets goal |
Also due today: Attach your annotated gel reading to your Unit 4 PLTW tracker and submit it 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.