We describe a family in which a-thalassemia occurs in association with a deletion of 62 kilobases from a region RNA analysis.

We describe a family in which alpha-thalassemia occurs in association with a deletion of 62 kilobases from a region upstream of the alpha globin genes. DNA sequence analysis has shown that the transcription units of both alpha genes downstream of this deletion are normal. Nevertheless, they fail to direct alpha globin synthesis in an interspecific hybrid containing the abnormal (alpha alpha)RA chromosome. It seems probable that previously unidentified positive regulatory sequences analogous to those detected in a corresponding position of the human beta globin cluster are removed by this deletion.

A Chinese family has been studied in which two siblings have haemoglobin Q-H disease. Using a combination of haematological and haemoglobin analysis, globin chain synthesis, analysis of alpha/beta globin messenger RNA ratios and restriction endonuclease mapping, it has been shown that each of these siblings has received one chromosome on which both alpha chain genes have been deleted and another on which there is only a single alpha chain locus which carries the alpha Q mutation. Their genotype is thus --/-alpha Q. Despite the fact that the haemoglobin Q mutation in this family is carried on a chromosome with a single alpha chain locus, heterozygous carriers for the variant have only 25% or less haemoglobin Q. Our observations indicate that the molecular basis for haemoglobin Q-alpha thalassaemia is similar to that for the common form of haemoglobin H disease in Orientals. Furthermore, they provide clear evidence that the level of an alpha chain variant in heterozygous carriers is not a reliable reflection of the number of alpha globin genes.

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Monosomy 7 was the sole karyotypic abnormality seen in a case of biphenotypic leukaemia involving both the myeloid and lymphoid lineages and in a case of de novo ALL undergoing a phenotypic shift to acute myeloid leukaemia at relapse. These observations suggest that monosomy 7 can be associated with transformation of a common lymphoid-myeloid progenitor cell.