Chapter 6: Sex Chromosomes and Sex Determination

Concepts

• Sexual differentiation plays a varying role in the life cycle of organisms
• X and Y chromosomes were first linked to sex determination early in the 20th century
• The Y chromosome determines maleness in humans
• The ratio of males to females in humans is not 1.0
• Dosage compensation prevents excessive expression of X-linked genes in humans and other mammals
• The ratio of X chromosomes to sets of autosomes determines sex in Drosophila
• Temperature variation controls sex determination in reptiles