What determines the gender of an offspring in sexually reproducing organisms?

The gender of an offspring in sexually reproducing organisms is determined by the presence of specific sex chromosomes, namely the X and Y chromosomes. In humans and many other organisms, females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

During fertilization, when a sperm cell (which can carry either an X or a Y chromosome) merges with an egg (which always carries an X chromosome), the combination of these chromosomes determines the sex of the offspring. If the sperm carries an X chromosome, the resulting zygote will be XX, and thus female. If the sperm carries a Y chromosome, the zygote will be XY, resulting in a male offspring. This chromosomal distinction is foundational in genetics and plays a crucial role in the determination of biological sex at conception.

Other options, such as somatic chromosomes, gene mutations, and environmental factors, do not play a direct role in determining the gender at the point of fertilization. Somatic chromosomes refer to the non-sex chromosomes that make up the rest of the organism's genetic material, while gene mutations can affect traits but do not dictate the sex directly. Environmental factors may influence the development or expression of sex characteristics, but they do not determine