Sex-determination system
A genetic, environmental, or combined mechanism that determines an organism’s sex or reproductive role.
Chromosomal sex determination: A system in which sex is associated with an organism’s chromosome complement. It describes systems such as XX/XY and ZZ/ZW, where chromosome differences guide sexual development.
Human sex determination: The developmental process by which genetic, gonadal, hormonal, and anatomical sex traits arise in humans. Humans provide a familiar example of an XX/XY system with developmental variation.
Sex differentiation: The developmental process through which sex-specific traits and reproductive structures form. Determination initiates or biases a pathway; differentiation builds its anatomical and physiological outcomes.
Evolution of sex-determination systems: The evolutionary study of how mechanisms assigning sex arise, change, and are replaced. Different systems across related species raise questions about why determining mechanisms turn over.
Genic sex determination: A system in which particular genes determine sex without sex-specific chromosomes. It separates the determining genes from chromosome combinations that characterize many familiar systems.
Bird sex determination: Sex determination in birds, typically involving female ZW and male ZZ chromosome complements. The reversed heterogametic sex contrasts with the common mammalian XX/XY pattern.
Sexual dimorphism: Differences in traits between males and females of the same species. Dimorphism describes resulting differences, not the mechanism assigning sex.
Sex chromosome evolution: The evolutionary processes that produce and transform chromosomes associated with sex determination. It explains how a determining locus can become linked to an increasingly differentiated chromosome.
Temperature-dependent sex determination: A system in which incubation temperature influences an individual's sexual development. It shows how an environmental cue can replace or modify chromosomal control.
Turtle sex determination: Sex determination in turtles, which may depend on incubation temperature or sex chromosomes, depending on the species. Turtles show that even one animal group can contain distinct sex-determining systems.