Question

The maleness of a child is determined by
A.The X chromosome in the zygote
B.The Y chromosome in zygote
C.The cytoplasm of germ cell which determines the sex
D.Sex is determined by chance

Answer 1

A zygote is a union of sperm cell and the egg cell which begins as a single cell and rapidly divides to form an embryo. A zygote is also called a fertilized cell.

Complete answer:
The zygote is a eukaryotic cell formed by the fertilization of male sperm with a female egg. The genome of a zygote is a combination of DNA of each gamete. It contains all the genetic information necessary to form a new individual. The zygote is the earlier]st developmental stage in multicellular organisms.
Let us analyze the options to find out the correct option.

Option A: The male zygote has XY genotype of which X comes from the mother egg and Y from the father’s sperm. Thus, the X chromosome in the zygote does not determine the maleness of the zygote. Therefore, this is the incorrect option.

Option B: The male zygote has XY genotype of which X comes from the mother egg and Y from the father’s sperm. The females always contribute the X chromosome while the male sperm might have X or Y chromosome. Here the Y chromosome is from the father’s sperm. Therefore, this is the correct option.

Option C: The chromsomal conititution of the germ cell determines the sex of the offspring. Cytoplasm of the germ cell do not contribute in sex determination of the zygote. Therefore, this is the incorrect option.

Option D: Sex is never determined by chance. It depends on which chromosome of the male fertilizes the X chromosome of the female egg. Therefore, this is the incorrect option.

Hence, the correct answer is option (B)

Note: The zygote is the earliest developmental stage in multicellular organisms. There is always 50% chances that the zygote will be a male and 50% chances that it will be a female based on which male chromosome fertilizes the egg.