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Question
Explain the mechanism of sex determination in birds.
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Solution
- In birds, the chromosomal mechanism of sex determination is ZW-ZZ type.
- In this type females are heterogametic and produce two types of eggs; 50% of eggs carry Z-chromosome, while 50% of eggs carry W- chromosome.
- Males are homogametic and produce one type of sperms. Each sperm carries a Z chromosome.
- Thus, the sex of an individual depends on the kind of egg (ova) fertilized by the sperm.
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Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environmental ones, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However in human beings, the sex of an individual is largely determined genetically.
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OR
Draw a flow chart to show that sex is determined genetically in human beings.
