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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.
In veterinary practice, fibroscopy is used under general anaesthesia in birds such as parrots. [3] Molecular sexing is a set of techniques that use DNA for determining sex in wild or domestic species [4] (population studies, farming, genetics) or humans (archaeology, forensic medicine [5]). Markers commonly used include amelogenin, SRY and ZFX/ZFY.
Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are energetically costly attributes that signal competitive breeding ...
However, homologues to the avian DMRT1 gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination. More research must be conducted in order to determine the exact sex determining gene of the platypus.
The sex chromosomes of birds evolved separately from those of mammals and share very little sequence homology with the XY chromosomes. [41] As such, scientists refer to bird sex chromosomes as a ZW sex-determining system, with males possessing two Z chromosomes, and females possessing one Z chromosome and one W.
Research on the heritability of IQ inquires into the degree of variation in IQ within a population that is due to genetic variation between individuals in that population. There has been significant controversy in the academic community about the heritability of IQ since research on the issue began in the late nineteenth century.
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Sex-linked barring has been established as the dominant locus B by traditional mendelian genetics in the beginning of the 20th century. [3] The responsible gene was predicted to be located on the Z chromosome [7] [8] and since male birds are homogametic (ZZ), they can be either hetero- or homozygous for sex-linked barring.