Bridges discovered in 1922 that in some strains of Drosophila melanogaster, the female individuals were triploid.
All the chromosomes including the X chromosomes were in triplicate. These tripilid females were like normal diploid females and were fertile. When these are mated to normal diploid males the following kinds of progenies are obtained.
1. Triploid females:
They have all chromosomes including the sex chromosomes in triplicate (3 sets of autosomes + 3 X chromosomes)
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2. Normal diploid females:
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They have two X chromosomes and 2 sets of autosomes.
3. Diploid XXY females:
They have 2 sets of autosomes two X chromosomes and a Y chromosome. This individual is a functional female in spite of the presence of Y, as the ratio between autosomes and 2 X chromosomes are maintained. These are produced as a result of fertilization between an egg carrying 2 X chromosomes and a sperm carrying Y chromosomes.
4. Intersexes:
They have two X chromosomes but with 3 sets of autosomes; Here even though there are two X chromosomeg the individual does not function as a female as the ratio between autosomes and sex chromosomes is not the usual one 2X : 2 sets of autosomes.
5. Intersexes:
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They are morphologically indistinguishable from the above category (4), but genetically they have two X chromosomes, one Y chromosome and 3 sets of autosomes.
6. Normal males:
They have one X, one Y chromosome and two sets of autosomes.
7. Super females:
They have three X chromosomes, and two sets of autosomes. Here again, the ratio between autosomes and X chromosome is disturbed. An excess of X chromosome without an increase in autosomes will result in super females.
8. Super males:
These have one X, one Y and three sets of autosomes. Here there is increase in autosomes (which are supposed to carry genes for maleness) without increase in X chromosomes, hence the individual will be super male.
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Intersexes are sterile individuals as they cannot function either as male or as female. This is due to the disturbance of the normal ratio of one or two X chromosomes with 2 sets of autosomes. Supermales and super females are also sterile individuals.