Question

Which of the following is correct ?

• A. Henking discovered the small Y-chromosome
• B. Drosophila also shows XX-XY sex determination like human
• C. Birds have ZZ-ZW sex determination, where females are ZZ & males are ZW
• D. Grasshoppers show XX-XY sex determination

Answer 1

Answer: (B)

Hermann Henking discovered the X chromosome while studying insects in the early 1890s. The sex chromosomes in birds are opposite of that in humans. Human males are heterogametic (XY), females are homogametic (XX), in birds males are homogametic (ZZ) and females are heterogametic (ZW). The "W" is the sex determining chromosome just as the Y in humans. A bird with a W is always a female. In grasshoppers, there is no Y chromosome, so a grasshopper with one X chromosome (symbolized as XO) is normally a male, while a grasshopper with two X chromosomes (XX) is normally a female.