Repeated sequences hypervariable

More recently a different DNA fingerprinting procedure has been described [A. J. Jeffreys etal. Nature 354 (1991) 204-209] based on sequence variation in hypervariable loci rather than the number of tandem repeats that are present. It has been applied successfully to hypervariable locus D1S8 and overcomes many of the limitations of conventional DNA fingerprinting. 

Investigations of the structure of monoclonal proteins have revealed the repeated occurrence of polypeptide chains with identical structure. For example, several monoclonal X chains, derived from individual BALB/c mice bearing plasma cell tumors, have been shown to possess identical amino acid sequences. These identical X chains occurred in combination with H chains of different classes or as free Bence Jones proteins (77-79). In addition to eight identical X chains, four others were found which differed in sequence in the V region by 1-3 amino acid residues (1-4 nucleotide interchanges in the DNA). All interchanges occurred in the hypervariable regions of the chain (near positions 30,50 or 95) (78, 79). 

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