In case, the female has heteromorphic ( ZW ) sex chromosomes and the male has homomorphic (ZZ) sex chromosomes. Thus, peacock shows ZZ/ZW sex determination type. In platypus, the sex determination is of XX-XY type. Both male and females has ten sex chromosome each. The male has XY, XY, XY, XY, XY and female has XX, XX, XX, . In snails, the sex determination is environmentally induced, while in cockroaches it is of types. In this type Y-chromosome is completely lacking. In this the presence of unpaired X-chromosomes determines the masculine sex.

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