Christmas Factor: Dosage Compensation and the Production of Blood Coagulation Factor IX

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Science  25 Jan 1963:
Vol. 139, Issue 3552, pp. 348-349
DOI: 10.1126/science.139.3552.348


The amount of factor IX (Christmas factor) for different genotypic classes was determined by means of a variant of the thromboplastin generation test. The mean value for females heterozygous for the Christmas gene was about half the mean values for normal males and for normal homozygous females; means for the latter two groups were about equal. This dosage compensation is interpreted as evidence in support of Lyon's hypothesis, according to which one X chromosome is inactive in mammalian females.