An unusual G-negative band within 1qh region a rare variant or an abnormality?
Morphological variations due to heterochromatic DNA of the secondary constriction region (qh) of human chromosome 1 are considered normal. The structural abnormalities involving or in association within the qh region have been difficult to characterize by routine cytogenetic methods and in turn have often gone undetected. In the past, the presence of a G-negative band within the qh region of chromosome 9 has been considered as a rare or unusual variant. Fortuitously, we were referred two cases where a G-negative band was embedded within the secondary constriction region of chromosome 1. Whole chromosome #1 specific painting probe, did hybridize to the band. Both patients have speech delay. Unfortunately, the parents were not available to confirm the mode of inheritance, nor could a definite conclusion be reached concerning its morbidity. Nevertheless, we are tempted to hypothesize that this is an unusual variant where a G-negative band apparently became genetically inert when it was sandwiched between two blocks of heterochromatin. Similar to a rare variant of chromosome 9 it could be found in the qh region of chromosome 16 as well, whose clinical consequences remain obscure.
Verma
R S
RS
Division of Genetics, Long Island College Hospital, SUNY Health Science Center, Brooklyn 11201-5514, USA.
Kleyman
S M
SM
Conte
R A
RA
D002675:Child, Preschool; D002869:Chromosome Aberrations; D002871:Chromosome Banding; D025063:Chromosome Disorders; D002878:Chromosomes, Human, Pair 1; D005260:Female; D014644:Genetic Variation; D006570:Heterochromatin / Q000235:genetics; D006801:Humans; D007621:Karyotyping
D006570:Heterochromatin