Frequency and types of deletional alpha+-thalassemia in northern Sardinia.

We determined by restriction mapping the frequency of the -alpha 3.7 determinant in a random sample of 48 adults in Northern Sardinia. We found a frequency of 0.18 +/- 0.04 and demonstrated that only type I crossover as determined by Apa I digestion (Higgs et al. 1984) is present. Moreover, we showed that this haplotype is not associated with an Rsa I polymorphism 5' to the alpha 2-globin gene. These data support the hypothesis of a unique origin of this deletion in Sardinia.