Mechanisms for the expression of parental alleles of the Gpd locus in mule erythrocytes
Serov, O.L.; Zakiian, S.M.; Kulichkov, V.A.
Genetika 13(10): 1761-1766
1977
ISSN/ISBN: 0016-6758 PMID: 612485 Document Number: 111525
The pattern of erythrocyte glucose-6-phosphate dehydrogenase (G6PD) was studied in 74 mules (42 females and 32 males) and in parental species (35 donkeys and 10 horses) by means of starch gel electrophoresis. The structural gene for G6PD, referred to as Gpd, is localized in horse and donkey X-chromosomes. Quantitative expression of parental alleles by Gpd locus in mule females varies within a wide range from hemizygous expression of the maternal allele to hemizygous expression of the paternal allele. Random inactivation of parental X-chromosomes is evident in female mules. In the majority of female mules studied, no selective preference among blood red cells or any certain cell population with an active maternal or paternal X-chromosome was found. The phenotypic variety of parental allelic expression is supposed to be connected with correlations casually formed in early development between cells with active maternal or paternal X-chromosome in the group of initiator (stem) cells of which definite blood system develops. The estimation of initiator cell number for blood red cell system gave values of 6-7, which is similar to the number of such cells in man and in fox hybrids. The number of initiator cells is supposed to vary in some individuals due to different duration of determination process, or different rate of initiator cells division in the course of determination. Expression and penetrance parameters of the genes located in X-chromosomes of mammals are determined by the number of initiator cells which give rise to different types of definite organs and tissues.