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Question
Differentiate between 'ZZ' and 'XY' type of sex-determination mechanisms.
Solution
The differences between ZZ and XY type of sex-determination mechanisms are listed below:
| ZZ Sex-Determination Mechanism | XY Sex-Determination Mechanism |
| In this type of chromosomal sex determination mechanism, the females are heterogametic, that is, they produce two types of gametes, while the males are homogametic. | In this type of chromosomal sex determination mechanism, the males are heterogametic, that is, they produce two types of gametes, while the females are homogametic. |
| Here, the females produce two types of eggs (A+Z) and (A+W), while the males produce only one type of sperm (A+Z). |
Here, the males have an X chromosome and its counterpart Y chromosome, which is distinctly smaller. Hence, the males are XY. However, females have a pair of X chromosomes; therefore, they are XX. |
| Organisms that have the ZZ type of sex-determination mechanism are birds, fishes, some reptiles, etc. | Organisms that have the XY type of sex-determination mechanism are humans and Drosophila. |
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