Red blood cell (RBC) size distribution for family 6 hemizygous proband and heterozygotes. (—•—) Relative frequency of a particular RBC cell size (----); range of RBC size distributions of normal individuals. MCV is indicated for each individual. (A) Profile for family 6 proband II.4 (XLSA genotype and pedigree numbers are from Table 1). (B) Profile for the proband’s sister, II.3. (C) Profile for the proband’s niece, III.7. (D) Profile for proband’s mother, I.1.