The X:A ratio is the ratio between the X chromosome and the number of sets of autosomes in an organism.
This ratio is used primarily for determining sex of drosophila flies. 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 triploid drosophila that has XXX, the ratio is 1:1 (3 Xs to 3 autosomes, since it is a triploid). For a diploid drosophila that has XY, the ratio is 1:2 (1 X to 2 autosomes, since it is diploid).
Famous quotes containing the word ratio:
“People are lucky and unlucky not according to what they get absolutely, but according to the ratio between what they get and what they have been led to expect.”
—Samuel Butler (1835–1902)