The quantitative expression of delta and beta human globin genes is controlled by both 5' and 3' untranslated regions.

The basis for the wide difference in the amounts of haemoglobins A and A2 found in normal human blood is not yet known. By analysing existing data on the levels of haemoglobins Lepore, anti-Lepore, and the recently discovered haemoglobin Parchman, resulting from a double cross-over within the delta-beta region, it is shown that regulation of the expression of these genes must take place at sites located within both their 5' and 3' untranslated regions.