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Lack of evidence that inactivation of the mouse X-chromosome is incomplete

Published online by Cambridge University Press:  14 April 2009

Mary F. Lyon
Mary F. Lyon
Affiliation:
Medical Research Council Radiobiological Research Unit, Harwell, Berkshire, England
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The fact that the X-linked genes scurfy (sf) and sparse-fur (spf) of the mouse do not produce a mosaic effect in heterozygotes had been taken, by other workers, together with results from X-Autosome translocations, as evidence that inactivation of the mouse X was incomplete. In this paper it is argued that absence of a mosaic effect is not adequate evidence that a gene is not inactivated. The argument was backed by an experiment in which the spf gene was introduced heterozygously into females carrying an X-linked translocation resulting in non-random X-inactivation with the same X active in all cells. When the mutant (spf) allele was on the active X its effect was fully expressed, indicating that the normal allele on the structurally normal inactive X was undergoing inactivation. Argument is further presented that results from X-Autosome translocations do not indicate the degree of completeness of inactivation in a structurally normal X. Hence, there is no evidence that inactivation of the mouse X is incomplete, although evidence from XO females does suggest that it may be incomplete in man.

Type
Research Article
Information
Genetics Research , Volume 8 , Issue 2 , September 1966 , pp. 197 - 204
Copyright
Copyright © Cambridge University Press 1966

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