SDSPAGE and Molecular Systematics

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SDS-PAGE and Molecular Systematics
Reconstructing Fish Phylogeny
M. Gillilland
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What is SDS-PAGE?

• SDS (Sodium dodecyl sulphate) is a detergent used
  to denature proteins
• PAGE (Polyacrylamide Gel Electrophoresis)

SDS-PAGE is one of many techniques that can be
used to determine the degree of relatedness
between 2 or more species
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Evolutionary Implications

• Assumption closely related species will have
• more proteins in common
• Phylogeny (Evolutionary History)
• Evolutionary Tree

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Protein Structure

• Primary structure
• Due to specific amino acid (aa) sequence

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Secondary structure Due to attraction between
specific aas in the sequence (hydrogen
bonds) Form ?-helix or ?-pleated sheets
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Tertiary structure Secondary folding due to
interactions of R groups (e.g.
disulfide bridges)
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Quaternary structure Two or more polypeptide
chains (e.g. hemoglobin)
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Fish Muscle Proteins

• Muscles contain many proteins
• Actin and Myosin
• Form muscle fibers that allow muscles to contract
  and relax
• Most common muscle proteins in all animals
• SDS-PAGE allows proteins to be sorted by size and
  identified

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Evolutionary Implications Revisited

• Assumption closely related species will have
• more proteins in common
• Phylogeny (Evolutionary History)
• Evolutionary Tree

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Evolutionary Tree
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Making Trees
Molecular Genetics
Morphology
mtDNA Cytochrome oxidase
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Evolutionary Relationships
Tuna/ Mackerel
Salmon/Trout
Cod
Catfish
Flounder
Shark
Scallop
Metazoa
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SDS-PAGE In Lab Getting at those fish proteins

• Functional fish proteins are treated with a SDS
  and heat
• SDS will make all protein molecules negatively
  charged
• Heat denatures the proteins
• Treatment allows the proteins to sort by size

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SDS-PAGE
Cathode
Anode