Question

In this type of questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as :
Assertion : Drosophila flies can be subjected to a contact with pure $C{O}_2$ for long hours, without injury.
Reason : $C{O}_2$ insensitivity is due to sigma factor.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (D)

Normal strains of Drosophila do not show sensitivity towards pure $C{O}_2$. L, Heritier and Teisser $(1958)$, however, discovered a true breeding strain of Drosophila which was sensitive to $C{O}_2$. Sensitive mother always give sensitive progeny, sensitive fathers rarely give sensitive progeny if the mother is normal. This sensitivity can be attributed to a virus like particle called sigma found in cytoplasm of the cells of a sensitive fly. Sigma factor is transmitted through egg cytoplasm and its reproduction depends on initial supply and on suitable temperature of $20^{\circ }C$, because it is heat labile at high temperature.