Sex Determination - Sex Determination in Some Insects

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Notes

Sex determination in some Insects:

  • A large number of insects are observed to have 'XO type' of sex determination mechanism.
  • In this type of sex determination, females will possess two X-chromosomes (XX) thereby are known as homogametic females.
  • Whereas males possess only one X-chromosome and are known as Heterogametic males.
  • Heterogametic males contain XO chromosomes in which O or Zero represents the absence of another X-chromosome.
  • 'O' will not determine the sex of organisms  (i.e., autosomes).
  • If the X carrying ovum is fertilized by the X carrying sperm, the resulting zygote XX will develop into a female.
  • If the sperm carrying no chromosome unites with the ovum, the zygote XO will develop into a male.

    XX-XO Type of Sex Determination

  • XX-XO types of sex determination are examples of male heterogamety as the males produce two types of gametes during meiosis. One with the X chromosome and another devoid of the chromosome.
  • Roundworms and some insects (true bugs, grasshoppers, cockroaches, etc.) exhibit 'XX-XO type' of sex determination.
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