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Encyclopedia > Testis determining factor

Testis-determining factor (TDF) is a general term for the gene (or product thereof) that results in maleness in humans and some other species. For other uses, see Gene (disambiguation). ... Look up Sex in Wiktionary, the free dictionary The members of many species of living things are divided into two or more categories called sexes (or loosely speaking, genders). ...


Certain genes cause chemical reactions that result in the development of testes. Embryos are gonadally identical, regardless of genetic sex, until a certain point in development; then the testis-determining factor causes male sex organs to develop, while lack of this factor will cause the embryo to develop as physically female. Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... For other uses, see Embryo (disambiguation). ... The gonad is the organ that makes gametes. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... Look up Female in Wiktionary, the free dictionary. ...


The TDF factor is encoded by the SRY gene located in the Y chromosome. It is a DNA binding protein, that enhances other transmission factors, or is a transcription factor itself. Its expression directly or indirectly causes the development of primary sex chords, which will later develop to seminiferous tubules. These chords form in the central part of the undifferentiated-yet gonad, turning it into a testis. The testis then starts secreting testosterone and the Mullerian Inhibiting Substance. This article is about the SRY gene. ... For other uses, see Gene (disambiguation). ... The human Y chromosome is one of two sex chromosomes, it contains the genes that cause testis development, thus determining maleness. ... DNA replication Deoxyribonucleic acid (DNA) is a nucleic acid which carries genetic instructions for the biological development of all cellular forms of life and many viruses. ... Gene expression, or simply expression, is the process by which the inheritable information which comprises a gene, such as the DNA sequence, is made manifest as a physical and biologically functional gene product, such as protein or RNA. Several steps in the gene expression process may be modulated, including the... This article needs to be wikified. ... The gonad is the organ that makes gametes. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... Testosterone is a steroid hormone from the androgen group. ... Anti-Müllerian hormone (AMH) is a dimeric glycoprotein that inhibits the development of the Müllerian ducts in a male embryo. ...


Older texts discuss the role of the HY antigen in the control of testicular development, but this was later disproven.


Role in disease

The TDF gene has some interesting implications. The genetic recombination of Crossing over can cause the gene to be transferred on to the X chromosome. In this case, the X chromosome will initiate testis development, so regardless of whether the person has a Y chromosome, the person will turn into a boy. Though everything else will be developed as if it were a girl (other sex related alleles), the apparent sex will be male (a syndrome known as XX male syndrome). Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ... Thomas Hunt Morgans illustration of crossing over (1916) Homologous Recombination is the process by which two chromosomes, paired up during prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. ... XX male syndrome (also called de la Chapelle syndrome) is a rare sex chromosomal disorder in men. ...


Conversely, such a cross-over event also can result in a Y chromosome that is missing its TDF, replaced with the corresponding sequence from the end of the X chromosome. Individuals who inherit this Y chromosome will develop as females, despite having the normal male chromosomal set of one X and one Y. However, the lack of two X-chromosomes gives complications to such females, called Turner syndrome.


See also


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