Single-base substitutions give rise to a five-banded DNA profile at the D10S28 locus.
BACKGROUND
DNA profiles from variable number of tandem repeat (VNTR) loci typically are composed of two bands, one derived from each member of the homologous pair of chromosomes. DNA profiles composed of more than two bands result from mutations, and the question arises as to the mechanism underlying these unusual multi-banded DNA profiles.


METHODS
An alleged father in a paternity test was found to have a five-banded DNA profile at the D10S28 locus when his DNA was subjected to single-locus restriction fragment length polymorphism mapping with the restriction enzyme Pvu II.


RESULTS
Several results suggest that this complex DNA profile is the result of several single-base changes within the VNTR locus. First, there was no evidence of partial digestion of the DNA with Pvu II. Furthermore, the multi-banded allele happened, in this case, to be transmitted to the child, who also showed a five-banded pattern composed of four bands inherited from the alleged father and one band inherited from the mother. Second, digestion of this DNA with Hae III resulted in the visualization of just two bands at the D10S28 locus.


CONCLUSIONS
The results confirm the notion that mutations at VNTR loci are not always the result of additions or deletions of tandem repeats, but that they can also involve single-base substitutions either within or flanking VNTR loci that give rise to atypical DNA profiles and new alleles at the locus.
Allen
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H.A. Chapman Institute of Medical Genetics, Children's Medical Center, Tulsa, Oklahoma.
Sanford-Sharp
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CE
D002871:Chromosome Banding; D004247:DNA / Q000097:blood / Q000235:genetics*; D016172:DNA Fingerprinting; D005260:Female; D006801:Humans; D007962:Leukocytes / Q000737:chemistry; D008297:Male; D010290:Parents; D012091:Repetitive Sequences, Nucleic Acid
D004247:DNA