Question

In Melandrium, sex determination is of
A. XX-XO
B. ZZ-ZW
C. XX-XY
D. XY-XO

Answer 1

Hint: Melandrium album is dioecious plant. It belongs to family Caryophyllaceae and has diploid number of chromosomes which is 24(n=12).It has heteromorphic sex chromosomes.

Complete answer:
1.Warmke H.K.(1946) was first to promote the sex determination method in Melandrium album.
2.It was observed that there was one pair of chromosomes that differed from another in both the sexes.
3.Female members of melandrim has same type of chromosomes while male has different pair of sex chromosomes.
4.The two members of the female chromosomes were the same like one of the chromosomes of male.
5.The chromosome which is present in females as well as in male is X-chromosome.
6.The sex chromosome of male which differ than the female is Y- chromosome.
7.The male is heterogamitic sex, produce two kinds of gametes which are with X and Y chromosomes and the female is homogametic sex , producing only one type of egg , all with X chromosomes.
8.In melandrium, Sex of the offspring depends on the kind of male gamete fertilizing the female gamete.
9.The offspring will be male if the fertilization takes place by male gamete carrying Y-chromosome and the offspring will be female if the male gamete carries X- chromosome.

Hence, the correct answer is option (C)

Note: Many organism has XX-XY sex determination system such as some plants of angiosperm like Lychnis , insects, reptiles and all mammals including humans also. Here X and Y are called sex chromosomes or even allosomes. And the remaining ones which are same in both the sexes are called autosomes. X chromosome is shorter than the Y chromosome.