When a woman becomes pregnant, the outcome of that pregnancy depends on many things—including a crucial event that happened while she was still growing inside her own mother's womb. It depends on the ...

Sex is determined in a variety of different ways throughout the animal kingdom. In mammals, it is determined genetically, not by temperature, as it can be in reptiles. Typically, females have two X ...

Chromosomes are tightly coiled structures in each of your cells that contain DNA, the code for all life. DNA is organized in segments on chromosomes called genes. Humans typically have 46 chromosomes ...