Molecular Evolution post-lab

Introduction to Molecular Evolution Post Lab

Purpose: To compare four fish species included in the lab (salmon, Atlantic salmon, Sambo salmon, trout sperm trout, lesser spotted dogfish, common European eel). Focus: Morphological characteristics based on available images and common names.

Aim of the Practical

  • Create two cladograms comparing fish species:

    • One based on morphological analysis.

    • One based on molecular analysis of fish muscle proteins.

Skills Developed:

  • Morphological observation and reasoning for cladogram creation.

  • Application of SDS protocol for muscle protein investigation.

  • Refining morphological cladogram with molecular data.

Cladograms Overview

  • Definition: Diagrams that represent evolutionary relationships based on shared ancestry.

  • Tree Structure:

    • Common ancestors connecting various species through branch points, indicating speciation events.

    • Each branch point corresponds to time progression from ancient to recent.

  • Interpretation:

    • Each species presents a unique and shared evolutionary history indicated by branched lines.

Morphological Characteristics Examined

  • Key Traits for Comparison:

    • Number and position of fins.

    • Body shape and size.

    • Jaw shape and sensory structures (e.g., eyes, gills).

    • Types and characteristics of scales.

  • Example Tables:

    • Simple and detailed versions produced by students.

    • Observations included sharp teeth in salmon and trout, rough fish skin.

Drawing Cladograms Based on Morphology

  • Student Findings: Different interpretations led to varied but generally consistent cladograms.

  • Example Results:

    • A group determined the dogfish (shark) as least related to salmon and trout.

    • Variability due to anatomical examination limitations.

Protein Analysis Using SDS-PAGE

  • Procedure Overview:

    • Extracted muscle tissue to analyze muscle proteins.

    • Denatured proteins and visualized using electrophoresis gel staining.

  • Protein Standard:

    • Known molecular weights used to identify protein sizes on the gel.

    • Smaller proteins travel further up the gel, allowing size comparisons across samples.

  • Band Comparison in SDS-PAGE Results

    • Focused on shared bands between species.

    • Analysis of bands between 25 kilodalton and 37 kilodalton markers.

    • Observations:

      • Variability in shared bands counted due to staining difference.

      • General trend: organism four had the fewest shared bands.

Molecular Cladograms Development

  • Molecular data typically provides more accurate cladograms than morphological data alone.

  • Directionality in drawing cladograms matters (past at the bottom, present at the top).

  • Example Interpretation:

    • Dogfish had the fewest shared bands; trout and salmon had the highest.

Taxonomic Relationships

  • Fish Classification:

    • Eels, trout, and salmon are ray-finned bony fish; dogfish is a cartilaginous fish.

    • Taxonomic confusion regarding the umbrella term "fish."

    • Lobe-finned fish related to tetrapods, showcasing evolution from aquatic to terrestrial life.

Conclusions of Practical Work

  • Fish as a taxonomic group can be misleading due to diverse ancestral lines.

  • Importance of both morphological and molecular data for accurate evolutionary representation.

  • Molecular data can minimize biases from convergent evolution.

SDS-PAGE Considerations and Techniques

  • Molecules can be analyzed for mass estimation by examining mobility on gels.

  • Protein purification processes include chromatography techniques.

Feedback and Suggestions for Future Work

  • Acknowledgment of experimental errors is crucial for transparency and learning.

  • Emphasis on continuous self-analysis during practical tasks; utilize feedback points available.

  • Proposed investigations may include exploring disease proteins, human evolutionary history, etc.

Additional Techniques – Western Blotting

  • Proteins are transferred from gel to a membrane for specific detection.

  • Antibodies enable identification of proteins, enhancing sensitivity in complex protein samples.