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

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:

Chlamydomonas

Caenorhabditis elegans (C. elegans)

X and Y Chromosomes: Early Studies

1906 Edmund B. Wilson

and Protenor

X and Y Chromosomes: Early Studies

Wilson and Lygaeus

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

Chromosome Composition in Humans

Karyotype

XX XY