AbstractHemoglobin Casper is characterized by the substitution of cytidine for thymidine in condon 106 of the beta globin gene. This substitution results in the creation of a new restriction site for Msp I but not for the isoschizimer Hpa II. The restriction pattern following digestion with Msp I reveals a 9.9‐kb fragment not seen in normal individuals or following digestion of Casper DNA with Hpa II. This finding confirms the predicted base mutation and indicates that the cytidine in the newly acquired CpG site is methylate