gel electrophoresis       (JELL eh-LEK-troh-for-EE-sis)
The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.

hemoglobin       (HEE-moh-gloh-bin)
An iron-containing protein in red blood cells that reversibly binds oxygen.

point mutation
A change in the chromosome at a single nucleotide within a gene.

primary structure
The level of protein structure referring to the specific sequence of amino acids.

protein structure
The arrangement of protein molecules in one or several long chains, or polypeptides, of amino acids linked in a characteristic sequence.

secondary structure
The localized, repetitive folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages.

sickle-cell disease
A genetic disease characterized by an abnormal form of the blood pigment hemoglobin and sickle-shaped red blood cells.

tertiary structure       (TUR-shee-air-ee)
Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

quaternary structure       (KWAT-ur-nair-ee)
The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.