Further observations on the hairpin-tail (Thp) mutation in the mouse

SUMMARY The hairpin-tail allele ( T hp ) of brachyury ( T ) on chromosome 17 of the mouse is unique in that the phenotype of heterozygous offspring depends on which parent contributed the T hp .The present paper offers formal proof of this fact using the t h2 allele of T as a marker, and discusses possible modes of action of the hairpin allele.