On Thursday, May 8, students in Mr. Jeff Baker’s Ap Biology science class at Catholic Central participated in a unique hands-on lab using SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, a technique used to separate proteins based on their molecular weight, measured in kiloDaltons (kD).

SDS-PAGE is commonly used in research and college-level labs to analyze proteins, which play a central role in many biological processes. In this lab, students used the method to examine muscle proteins from five fish species: Atlantic salmon, rainbow trout, whitefish, Dover sole, and swordfish.

“This is the first time we’ve run this lab here at Catholic Central,” said Mr. Baker. “It’s a widely used technique in higher-level labs, and it’s been valuable for students to see how it works.”

Students focused specifically on myosin light chains, a type of muscle protein, and used the gel to generate protein “fingerprints” for each fish. These fingerprints appear as bands on the gel, which can be visually compared to identify similarities and differences between species.

In the attached photo below, the red box highlights the region of the gel containing the myosin light chains used for analysis.

By analyzing the banding patterns, students were able to make preliminary observations about evolutionary relationships. The results showed that salmon and trout shared the most similar protein profiles, indicating a close relationship. Swordfish had the fewest bands in common with the others, suggesting it is the out-group in the evolutionary tree. Whitefish showed more similarities with salmon and trout, while Dover sole appeared to fall in between whitefish and swordfish.

Next, the class will use the gel data to build a standard curve, allowing them to estimate the molecular weights of the protein bands. This will help confirm the evolutionary relationships among the fish species by comparing the masses of the myosin light chains.

“The data align with what we know about their environments,” Mr. Baker explained. “The three freshwater fish (salmon, trout, and whitefish) group more closely together, while the two marine fish (Dover sole and swordfish) are more distinct.”

While SDS-PAGE equipment is more commonly found in college or professional laboratories, Mr. Baker noted that the kits used in class have become more accessible to schools in recent years.

“I’m not sure how common it is at the high school level, but the company has offered this for a while. Still, it’s great that our students can gain experience with this type of analysis.”

Students will now compare their data-based evolutionary tree (clade) to current models of fish evolution and reflect on how molecular evidence supports biological relationships.

“This is the most effective way I’ve found to show evolutionary relationships using real data,” Mr. Baker said. “It’s been a solid introduction to how scientists explore these kinds of questions.”