X:A ratio
The X:A ratio is the ratio between the number of X chromosomes and the number of sets of autosomes in an organism. This ratio is used primarily for determining the sex of some species, such as drosophila flies and the C. elegans nematode.Script error: No such module "Footnotes".Script error: No such module "Check for unknown parameters". The first use of this ratio for sex determination is ascribed to Victor M. Nigon.Script error: No such module "Footnotes".Script error: No such module "Check for unknown parameters".
Generally, a 1:1 ratio results in a female and a 1:2 ratio results in a male. When calculating the ratio, Y chromosomes are ignored. For example, for a diploid drosophila that has XX, the ratio is 1:1 (2 Xs to 2 sets of autosomes, since it is a diploid). For a diploid drosophila that has XY, the ratio is 1:2 (1 X to 2 sets of autosomes, since it is diploid).Script error: No such module "Footnotes".Script error: No such module "Check for unknown parameters". Drosophilla sex chromosome ratio determines the factors it encodes which enhances the synthesis of sxl protein which in turn activates the female specific pathway.
See also
Notes
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References
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