[The C heterochromatin of chromosomes 1, 9, 16 and Y in patients with Noonan's syndrome].

A significant reduction in the total amount of C heterochromatin of chromosomes 1, 9, 16, and Y was detected in six patients with Noonan's syndrome. The results obtained do not contradict the results of our previous investigations of the correlation between a small amount of C heterochromatin and growth retardation. The clinical resemblance of Noonan's and Turner's syndromes with respect to the functional role of facultative and constitutive heterochromatin in early embryogenesis is discussed.