Fruitless (gene)

The '''fruitless gene' (fru) is a Drosophila melanogaster gene that encodes several variants of a transcription factor protein. Normal fruitless function is required for proper development of several anatomical structures necessary for courtship, particularly motor neurons which innervate muscles needed for sexual behaviors. The gene is not present in mammals. Research on fruitless'' has received attention in the popular press, since it is seen to be connected to the issue of the genetics of human sexual orientation, and behaviors such as gender-specific aggression.


Male flies with mutations in the fruitless gene display altered sexual behavior. Fruitfly courtship, which involves a complex male-initiated ritual, may be disrupted in a number of ways by mutated fru alleles; fru is necessary for every step in the ritual. Some alleles prevent courting entirely, while others disrupt individual components. Notably, some loss-of-function alleles change or remove sexual preference.

Although many genes are known to be involved in male courtship behavior, the fruitless gene is noteworthy because it exhibits sex-specific alternative splicing. When females produce the male-spliced gene product, they behave as males. Males with the female-spliced gene product exhibit complete loss of male courtship behavior and sexual orientation.

fruitless has at least four promoters, each encoding proteins with a beta-turn-beta domain containing a zinc finger motif. Alternative splicing occurs at both the 5' and 3' ends, and there are several variants (other than the male- and female-specific splicing patterns).


Early work refers to the gene as fruity, an apparent pun on both the common name of D. melanogaster, the fruit fly, as well as a slang word for homosexual. As social attitudes towards homosexuality changed, fruity came to be regarded as offensive, or at best, not politically correct. Thus, the gene was re-dubbed fruitless, alluding to the lack of offspring produced by flies with the mutation.

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