Question

Freshly released human egg has
A)One Y-chromosome
B)One X-chromosome
C)Two X-chromosome
D)One X-chromosome and one Y-chromosome

Answer 1

Hint: In humans, the ovum is released from the ovary in the secondary oocyte stage. Thus in human-being, ovulation is a process in which the ovum is released from the secondary ovary. The wall of the ovary gets ruptured to release oocytes. The mature ovum or a female gamete is a spherical shape.

Complete answer:
The human ovum is free from yolk so-known as an alecithal egg. Its cytoplasm is known as ooplasm that contains a nucleus termed as germinal vesicles. The nucleus comprises a prominent nucleolus. There is no centriole inside the ovum and the cytoplasm is enveloped by the plasma membrane (cytoplasm). There is a presence of a very small vesicle called cortical granules under the plasma membrane. Perivitelline space is present outside the plasma membrane. Just outer to perivitelline space, there is thick, noncellular zona pellucida which is secreted by follicular cells. Outer to zona pellucida, there is a very thick cellular layer of corona radiata. The side of the ovum which extrudes polar bodies is known as the animal pole. The opposite is known as the vegetal pole. The human ovum can be fertilized about 24 hours after ovulation. The egg released is haploid as it undergoes meiotic division of diploid primary oocyte having XX chromosome. There the egg always has one X chromosome.

Hence, the correct answer is option (B)

Note: The process of forming the ovum is known as oogenesis. During the maturation phase, after the first meiotic division, the primary oocyte divides into the secondary oocyte and first polar bodies. In humans, the ovum is released as a secondary oocyte which is haploid in nature i.e. having an X chromosome.