Question

Assertion :According to Genic Balance Theory, the karyotype with A A -XO in Drosophila is sterile female. Reason: Y-chromosome in Drosophila lacks male determining factor.

• A. Both (A) and (R) are true (R) is the correct explanation factor
• B. Both (A) and (R) are true (R) is not the correct explanation factor
• C. (A) is true, but (R) is false
• D. (A) is false, but (R) is true

Answer 1

The correct option is A Both (A) and (R) are true (R) is the correct explanation factor

• According to the genic balance theory, the karyotype with AA- XXY in Drosophila is a sterile female.
• The sex determination in Drosophila is XY method. The allosomes are X and Y chromosomes. Males and females have the same number of chromosomes i.e., 8. Of these, six are autosomes and two are allosomes.
• Female is AAXX and male is heterogametic AAXY, where A is the single set of autosomes. Calvin Bridge in 1916 showed that Y chromosome has no role in the determining of sex in Drosophila.
• He proposed that both the X chromosomes and autosomes together play a critical role in the determination of sex.
  So, the correct option is A.