Genetic sex determination is a biological process that dictates the sex of an organism based on its genetic makeup. In many species, including humans, this is primarily determined by the presence of specific sex chromosomes. For example, individuals with two X chromosomes typically develop as female, while those with one X and one Y chromosome develop as male. This mechanism varies across different organisms. In some reptiles and fish, environmental factors can influence sex determination, while in others, such as certain insects, it may depend on the number of X chromosomes present. Overall, genetic sex determination plays a crucial role in the reproduction and development of many species.