Question

In which of these the sex chromosome have discovered for the first time?
A. Melandrium
B. Nephrolepis
C. Pinus
D. Sphaerocarpus

Answer 1

Hint: The chromosome was discovered for the first time in red campion plants that have XX-XY mechanism of sex determination, wherever the male plant is heterogametic and carries “XY” chromosome while, the female plant carries 2 copies of X-chromosomes (XX) as sex chromosomes.

Complete answer:
The chromosome was discovered for the first time in Melandrium. These plants have XX-XY mechanism of sex determination, wherever the male plant is heterogametic and carries “XY” chromosome, while feminine plant carries 2 copies of X-chromosomes (XX) as sex chromosomes. Regardless of the quantitative relation of range of X–chromosomes to the line of autosomes, the presence of Y-chromosome determines male sex of the plant. Chromosomes aside from sex chromosomes area unit referred to as autosomes and area unit depicted by “A”. As is obvious from the independence of sex of plant to X/A quantitative relation, A-chromosomes don't seem to be sex determinant during this plant. Humans conjointly follow XX-XY mechanism where females are homogametic XX and males are heterogametic XY.
Hence, the correct answer is option A.

Additional information: Sex chromosomes are also known as allosomes, whereas an autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in autosome pairs which may have different structures.

Note: The six most typical Karyotypes are:
X: Roughly one in 2,000 to one in 5,000 individuals (Turner's)
XXY: Roughly one in 500 to one in 1,000 individuals (Klinefelter)
XYY: Roughly one out of 1,000 people.
XXXY: Roughly one in 18,000 to one in 50,000 births.