Assignment of the glucose-6-phosphate dehydrogenase (G6PD) gene to tammar wallaby chromosome Xq by fluorescence in situ hybridization with a BAC clone.

Comparative mapping, between marsupials and eutherians (divergence 180 mya), provides information about mammalian genome organization and evolution. G6PD is a key marker on the X chromosome in all mammals. It has been important for studies of X chromosome inactivation, being random in eutherians and paternal in marsupials. G6PD is a housekeeping X-linked gene that converts glucose into pentose sugars, whose bi-products prevent cellular oxidative stress. Numerous human variants exist and deficiencies cause severe anemia and newborn jaundice (Mehta et al., 2000). Older radiation in situ hybridization results placed G6PD on the distal third of Xq (Spencer et al., 1991) in the model marsupial Macropus eugenii (tammar wallaby). However, genetic linkage was established between G6PD and ribosomal RNA genes on the short arm, suggesting that G6PD is close to the centromere (McKenzie et al., 1996). This study maps G6PD by in situ fluorescent hybridization to a proximal position on the long arm of the tammar X chromosome. Fig. 1. FISH mapping of Me BAC G6PD to the long arm of the X chromosome just below the centromere (male metaphase).