A new method for detection of small modifications in genomic DNA, applied to the human δ‐β globin gene cluster

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Abstract
Cloned DNA fragments were subcloned in filamentous coliphages fd 103 or M 13; the recombinant single-stranded DNA were then used to form hybrids with genomic DNA, as well as with complementary recombinant, single-stranded DNA. Hybrids were submitted to S1-nuclease treatment, alone or in combination with restriction enzyme digestions. This method was used to analyze the .delta.-.beta. globin gene cluster from the total genomic DNA of a .beta.0-thalassemic patient. A modification located .apprx. 530 base pairs upstream from the cap site of the .beta.-globin gene was detected in only 1 thalassemic chromosome of this patient. Sequence analysis has shown that the patient was homozygous for a single nucleoside change (dC .fwdarw. dT) which remains undetected by the hybridization method, leading to a codon 39 nonsense mutation; they have also demonstrated that he was heterozygous for the modification mentioned and detected by S1-nuclease, which corresponds to an additional sequence d(T-A-T-A) in a 52 alternating purine-pyrimidine run, leading to a complex change from d[(A-T)7(T)7] to d[(A-T)11(T)3].
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