Question

In Melandrium, sex determination is of_____type.

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

Answer 1

Answer: (C)

XX - XY

Sex determination in birds is of ZW-ZZ types in which females are heteromorphic (ZW) and males have homomorphic sex chromosomes (ZZ). In round worms and few insects (grasshopper), XX-XO mechanism of sex determination is present where females are homogametic (XX) but the male carries only one sex chromosome (XO). Hence the male grasshopper carries XO sex chromosomes.

In Melandrium, XX-XY mechanism of sex determination is present where the male plant is heterogametic and carries “XY” sex chromosome while female plant carries two copies of X-chromosomes (XX) as sex chromosomes.

Human follows XY-XX mechanisms of sex determination wherein male is heterogametic and carries “XY” sex chromosome while female carries two copies of X-chromosomes (XX) as its sex chromosomes. The absence of part or full copy of one X-chromosome in the human female is "Turner Syndrome" but the "XO" condition is not female sex determinant.