A new mutation (t-int) interacts with the mutations of the mouse T/t complex that affect the tail.

A new recessive mutation affecting tail length is described. It is unlinked to the T/t-complex on chromosome 17 and yet it shows cumulative phenotypic effects with several t-complex mutations: T, TCu, tct and Fuki. It does not interact with five different nonchromosome 17 mutations that affect tail length. Thus, t-int is a tail modifier with surprisingly specific interactions.