Search results
Results From The WOW.Com Content Network
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
The XX/XY sex-determination system is the most familiar, as it is found in humans. The XX/XY system is found in most other mammals, as well as some insects. In this system, females have two of the same kind of sex chromosome (XX), while males have two distinct sex chromosomes (XY).
The XY sex-determination system is a sex-determination system present in many mammals, including humans, some insects , some snakes, some fish , and some plants (Ginkgo tree). In this system, the sex of an individual usually is determined by a pair of sex chromosomes .
In a large number of organisms, the sex-determination systems presently observed are products of sex chromosome turnover. Sex chromosome turnover is a process defined as when the type of the sex chromosome changes as a product of a change in the identity of the sex-determining genes (such as by mutation) or by a change in their location. [ 28 ]
[6] [7] The term "sex determination" increased in usage after 1900. [8] In the 1960 and early 70's the term "sex assignment" came into prominent use as a colloquially word for "determination of sex" and "sex determination". "Sex assignment" did not occur in writing prior to the 1960's. It is used ~100 times less frequently than "determination ...
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
Other organisms have mirror image sex chromosomes: where the homogeneous sex is the male, with two Z chromosomes, and the female is the heterogeneous sex with a Z chromosome and a W chromosome. [48] For example, the ZW sex-determination system is found in birds , snakes , and butterflies ; the females have ZW sex chromosomes, and males have ZZ ...
Temperature-dependent sex determination is believed by many to have been the ancestral sex determining mechanism. [7] In turtles, one study suggests that genetic sex determination has originated at least six times: in (1) trionychids, (2) chelids, (3) staurotypids, (4) emydids, and (5 and 6) twice in batagurids. [1]