''Doublesex'' (''dsx'') is a

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

that is involved in the

sex determination system A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most organisms that create their offspring using sexual reproduction have two sexes. In some species there are hermaphr ...

of many insects including the fruit fly ''

Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (the taxonomic order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly" or "pomace fly". Starting with Ch ...

''.

Sex determination

The gene is expressed in both male and female flies and is subject to

alternative splicing Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be ...

, producing the

protein isoform A protein isoform, or "protein variant", is a member of a set of highly similar proteins that originate from a single gene or gene family and are the result of genetic differences. While many perform the same or similar biological roles, some isof ...

s ''dsx^f'' in females and the longer ''dsx^m'' in males. The production of ''dsx^f'' is caused by the presence of the female-specific version of the ''transformer'' (''tra'') gene. In a sense, the isoform of ''dsx'' informs a cell about the organism's sex; for instance, female genitals only develop if ''dsx^f'' is present. In conjunction with the gene ''

fruitless The ''fruitless'' gene (''fru'') 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 nece ...

'', ''dsx'' also causes differences in the brain structure and behavior of males and females. Lay summary: Although the details of sex determination differ in the various species, there is a gene related to ''dsx'' in

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...

s (

DMRT1 Doublesex and mab-3 related transcription factor 1, also known as DMRT1, is a protein which in humans is encoded by the ''DMRT1'' gene. Function DMRT1 is a dose sensitive transcription factor protein that regulates Sertoli cells and germ cells ...

) and in

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s ( MAB-3). All of these are

transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The fu ...

s with a

zinc finger A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn2+) in order to stabilize the fold. It was originally coined to describe the finger-like appearance of a hypothesized struct ...

DNA-binding domain A DNA-binding domain (DBD) is an independently folded protein domain that contains at least one structural motif that recognizes double- or single-stranded DNA. A DBD can recognize a specific DNA sequence (a recognition sequence) or have a genera ...

(known as the

DM domain DM, Dm, dm, or D.M. may stand for: Academic titles and postnominals * Dame of the Sovereign Military Order of Malta, a chivalric order * Doctor of Management, an academic management degree * Doctor of Medicine, an academic medical degree * Docto ...

) and are involved in sex-specific differentiation.

References

{{reflist Drosophila melanogaster genes Insect proteins Sex-determination systems Developmental genes and proteins