A Totally Sex-linked Gene in the House Mouse

THE first clearly proved case of total sex-linkage in the house mouse has been found – a fact worthy of record since very few sex-linked genes are yet known in mammals other than man, and none in the rodents. Apart from man, where hæmophilia and colour-blindness are the best known of a number of more or less certainly sex-linked genes 1 , there are only yellow in cats 2 and hæmophilia in dogs 3 . In the mouse two genes, mottled and brindled , have been described 4 which may be totally sex-linked; but this cannot be directly proved as both genes are lethal in males. A test using females heterozygous for the new gene and for mottled or brindled should settle this point.