Fruitless (gene)
Encyclopedia
The fruitless gene is a Drosophila melanogaster
gene
that encodes several variants of a putative transcription factor
protein
. Normal fruitless function is required for proper development of several anatomical structures necessary for courtship, including motor neurons which innervate muscles needed for fly sexual behaviors. The gene does not have an obvious mammallian homolog, but appears to function in sex determination in species as distant as the mosquito Anopheles gambiae. fruitless serves as an example of how a gene or groups of genes may regulate the development and/or function of neurons involved in innate behavior. Research on fruitless has received attention in the popular press, since it provokes discussion on genetics of human sexual orientation
, and behaviors such as gender-specific aggression
.
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 has been considered noteworthy because it exhibits sex-specific alternative splicing
. When females produce the male-spliced gene product, they behave as males. Males that do not produce the male-specific product do not court females and are infertile.
fruitless has at least four promoters, each encoding proteins containing both a BTB (Broad complex/tramtrack/bric-a-brac) domain and 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). The fruitless gene locus also controls the expression of hundreds of other genes, any subset of which may actually regulate behavior.
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. However, despite the original name and a continuing history of misleading inferences by the popular media, fruitless mutants primarily show defects in male-female courtship, though certain mutants cause male-male or female-female courtship.
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
that encodes several variants of a putative transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
. Normal fruitless function is required for proper development of several anatomical structures necessary for courtship, including motor neurons which innervate muscles needed for fly sexual behaviors. The gene does not have an obvious mammallian homolog, but appears to function in sex determination in species as distant as the mosquito Anopheles gambiae. fruitless serves as an example of how a gene or groups of genes may regulate the development and/or function of neurons involved in innate behavior. Research on fruitless has received attention in the popular press, since it provokes discussion on genetics of human sexual orientation
Biology and sexual orientation
Biology and sexual orientation is the subject of research into the role of biology in the development of human sexual orientation. No simple, single cause for sexual orientation has been conclusively demonstrated, but research suggests that it is by a combination of genetic, hormonal, and...
, and behaviors such as gender-specific aggression
Aggression
In psychology, as well as other social and behavioral sciences, aggression refers to behavior between members of the same species that is intended to cause humiliation, pain, or harm. Ferguson and Beaver defined aggressive behavior as "Behavior which is intended to increase the social dominance of...
.
Function
MaleMale
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
flies with mutations in the fruitless gene display altered sexual behavior. Fruitfly courtship, which involves a complex male-initiated ritual
Ritual
A ritual is a set of actions, performed mainly for their symbolic value. It may be prescribed by a religion or by the traditions of a community. The term usually excludes actions which are arbitrarily chosen by the performers....
, 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 has been considered noteworthy because it exhibits sex-specific alternative splicing
Alternative splicing
Alternative splicing is a process by which the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing...
. When females produce the male-spliced gene product, they behave as males. Males that do not produce the male-specific product do not court females and are infertile.
fruitless has at least four promoters, each encoding proteins containing both a BTB (Broad complex/tramtrack/bric-a-brac) domain and a zinc finger
Zinc finger
Zinc fingers are small protein structural motifs that can coordinate one or more zinc ions to help stabilize their folds. They can be classified into several different structural families and typically function as interaction modules that bind DNA, RNA, proteins, or small molecules...
motif
Structural motif
In a chain-like biological molecule, such as a protein or nucleic acid, a structural motif is a supersecondary structure, which appears also in a variety of other molecules...
. Alternative splicing occurs at both the 5' and 3' ends, and there are several variants (other than the male- and female-specific splicing patterns). The fruitless gene locus also controls the expression of hundreds of other genes, any subset of which may actually regulate behavior.
Name
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 slangSlang
Slang is the use of informal words and expressions that are not considered standard in the speaker's language or dialect but are considered more acceptable when used socially. Slang is often to be found in areas of the lexicon that refer to things considered taboo...
word for homosexual. As social
Social
The term social refers to a characteristic of living organisms...
attitudes towards homosexuality changed, fruity came to be regarded as offensive, or at best, not politically correct
Politically Correct
Politically Correct may refer to:*Political correctness, language, ideas, policies, or behaviour seeking to minimize offence to groups of people-See also:*Politically Correct Bedtime Stories, book by James Finn Garner, published in 1994...
. Thus, the gene was re-dubbed fruitless, alluding to the lack of offspring produced by flies with the mutation. However, despite the original name and a continuing history of misleading inferences by the popular media, fruitless mutants primarily show defects in male-female courtship, though certain mutants cause male-male or female-female courtship.