Question

Sex determination in butterflies is:

• A. XX-XY type
• B. XX-XO type
• C. ZZ-ZW type
• D. ZZ-ZO type

Hint:

In birds and butterflies, females are heterogametic.
For butterflies specifically, remember that they predominantly show the ZZ-ZO mechanism, where females have one less chromosome than males.

Answer 1

The Correct Option is D

Step 1: Recall which sex is heterogametic in butterflies.
Unlike mammals where males carry the differing chromosome, in butterflies and most moths it is the female that carries the odd chromosome set.
Step 2: Recall what that odd set looks like.
Male butterflies carry two similar Z chromosomes, ZZ, while females carry only a single Z with no partner chromosome at all.
Step 3: Name the system.
Since females have just one Z and nothing else, this is written as ZZ-ZO, not ZZ-ZW where a distinct W chromosome would be present.
Final answer: Option 4, ZZ-ZO type.