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Question:

Which of the following is correct?

Henking discovered the small Y-chromosome.

Drosophila also shows XX-XY sex determination like humans.

Birds have ZZ-ZW sex determination, where females are ZZ and males are ZW.

Grasshoppers show XX-YY sex determination.

Solution:

The correct statement is: Henking discovered the small Y-chromosome.

Hermann Henking, in 1891, observed a peculiar structure in the nuclei of the cells of the insect Pyrrhocoris apterus. He noticed that this structure did not participate in meiosis, and he termed it the 'X body'. It was later recognized that this 'X body' was the Y chromosome. The other options are incorrect:

  • Drosophila also shows XX-XY sex determination like humans. While humans use an XX-XY system, Drosophila uses an XX-XO system, where males have only one X chromosome (XO) and females have two (XX).
  • Birds have ZZ-ZW sex determination, where females are ZZ and males are ZW. This is incorrect. In birds, the sex chromosomes are Z and W. Females are ZW, and males are ZZ.
  • Grasshoppers show XX-YY sex determination. This is also incorrect. Grasshoppers show an XX-XO sex determination system, similar to Drosophila.