Chromosome 4

Abstract

In the study of 7- and 8-year olds (Lubs et al., Population cytogenetic studies in humans, 1977), Q-band heteromorphisms consisting of level 4 and 5 intensities (Table 2.1) were seen in about 20% of the white children and 9% of the black children. C-band variants of 4cen were seen in approximately 7.6% of children overall with no significant racial difference. Verma and Dosik (Can J Cytol 23:315–320, 1981) found bright QFQ variants (levels 3 and 4) in 7% of American blacks. Bardham et al. (Clin Genet 20:44–47, 1981) found two types of common QFQ-band variants, one showing an intensely Q-bright band in 4cen and the other an intensely Q-bright band in proximal 4p. A higher frequency of Q-bright heteromorphisms reportedly found in patients with a variety of clinical problems has not been supported in subsequent studies (Docherty and Bowser-Riley, J Med Genet 21:470–472, 1984; Babu and Verma, Cytogenet Cell Genet 41:60–61, 1986). In a study of Q-band heteromorphisms for paternity testing (Olson et al., Am J Hum Genet 38:235–252, 1986), seven different variants were found in normal subjects (Fig. 9.1a).