Chromosomal polymorphisms of 1, 9, 16, and Y in 4 major ethnic groups: A large prenatal study

Using trypsin Gicmsa banding (GTG), major polymorphisms of the constitutive heterochromatin regions of chromosome 1, 9, 16, and Y were recorded in a New York City population. Polymorphisms were recorded from amniotic fluid specimens received from 6,250 patients from 4 major population groups, ic. White (European)–2,334 cases, American Black–1,795 cases, Hispanic descent–1,737 cases, and Asian (Oriental and Indian)–384 cases. The major chromosomal polymorphisms were classified as follows: obvious pericentric inversion of the constitutive heterochromatin of the long arm of the chromosome (inv qh); significantly enlarged heterochromatic region of the long arm (qh+ is greater than, or equal to, twice the size of the short arm of chromosome 16 [16p]); very small or deficient heterochromatic region in the long arm (qh−); large Y (Yq‐f > size of chromosome 18), small Y (Yq− < size of a G‐group chromosome), and pericentric inversion of Y. Our prenatal study con‐firmed that the incidence of specific chromosomal variants is different in each population group. The most striking examples of this are the pcricentric inversion of chromosome 9 and the different polymorphisms of the Y chromosome. The incidence of inv (9) is highest in the Black population (3.57%); slightly above average in Hispanics (2.42%); and relatively low in Whites (0.73%) and Asians (0.26%). The Y appears to be more variable in Asian (3.37%) and Hispanic (1.82%) than in White or Black groups. The 9qh+ is seen more frequently than lqh +, or 16qh+. Inv (1), 9qh−, and 16qh− are rare. There were no cases of either Iqh− or inv (16). Thus far, we are not aware of any deleterious phenotypic nor clinical effect of these chromosomal polymorphisms nor of any apparent association with fetal wastage.