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  4. ‘X0’ type of heterogametic males are seen in

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Q. ‘X0’ type of heterogametic males are seen in

JIPMERJIPMER 2015Principles of Inheritance and Variation

Solution:

XX - X0 type of sex determination is found in roundworms and some insects (grasshoppers, cockroaches etc.). In this type of sex determination, the females have two sex chromosomes, XX, while the males have only one sex chromosome, X. There is no second sex chromosome in males. Therefore, the males are designated as X0. The females are homogametic because they produce only type of eggs (A + X). The males are heterogametic with half the male gametes (gynosperms) carrying X-chromosome (A + X) while the other half (androsperms) being devoid of it (A + 0). The sex ratio produced in the progeny is 1 : 1.