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The XO sex-determination system (sometimes referred to as X0 sex-determination system) is a system that some species of insects, arachnids, and mammals use to determine the sex of offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (XO), while females have two (XX).
Some chromosomal sex determination systems in animals A sex-determination system is a biological system that determines the development of sexual characteristics in an organism . [ 1 ] Most organisms that create their offspring using sexual reproduction have two common sexes and a few less common intersex variations.
A large body of molecular evidence supports a variety of mechanisms for large evolutionary changes, including: genome and gene duplication, which facilitates rapid evolution by providing substantial quantities of genetic material under weak or no selective constraints; horizontal gene transfer, the process of transferring genetic material to ...
Animals with few offspring can devote more resources to the nurturing and protection of each individual offspring, thus reducing the need for many offspring. On the other hand, animals with many offspring may devote fewer resources to each individual offspring; for these types of animals it is common for many offspring to die soon after birth ...
Each of these offspring contains numerous genes which have coding for specific tasks and properties. Males and females both contribute equally to the genotypes of their offspring, in which gametes fuse and form. An important aspect of the formation of the parent offspring is the chromosome, which is a structure of DNA which contains many genes. [1]
Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as ...
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.
Sexual reproduction, where offspring result from the fusion of gametes from two parents, is the most common form of biparental inheritance. While less common, cases of biparental inheritance in extranuclear genes have been documented, such as biparental inheritance of mitochondrial DNA , or chloroplast DNA in plants. [ 1 ]