1. Chapter 5: Sex Determination Life cycles and reproductive modes *Asexual reproduction *Primary sexual differentiation *Secondary sexual differentiation *Unisexual, dioecious and gonochoric *Bisexual, monoecious and hermaphroditic *Alternation of generations *Sexual reproduction Some additional terms:

2. Sex Chromosomes: *Sex chromosomes *Autosomes Example: In Drosophila and all mammals sex chromosomes designated as X and Y XX=female XY=male *1909 Thomas Hunt Morgan II III IV XX XY or

3. Chlamydomonas

4. Caenorhabditis elegans (C. elegans)

5. X and Y Chromosomes: Early Studies 1906 Edmund B. Wilson and Protenor

6. X and Y Chromosomes: Early Studies Wilson and Lygaeus

7. X and Y Chromosomes: Early Studies Terms: Homogametic sex Heterogametic sex *The male is not always the heterogametic sex… Examples: Moths, butterflies, most birds, some fish, reptiles, amphibians, at least one species of plants

8. Chromosome Composition in Humans Karyotype XXXY