Chapter 5: Sex Determination

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Chapter 5 Sex Determination
Life cycles and reproductive modes Asexual
reproduction
Sexual reproduction
Alternation of generations
Some additional terms
Primary sexual differentiation Secondary sexual
differentiation
Unisexual, dioecious and gonochoric Bisexual,
monoecious and hermaphroditic
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Sex Chromosomes
1909 Thomas Hunt Morgan
Sex chromosomes Autosomes
Example In Drosophila and all mammals sex
chromosomes designated as X and
Y XXfemale XYmale
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Chlamydomonas
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Caenorhabditis elegans (C. elegans)
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X and Y Chromosomes Early Studies
1906 Edmund B. Wilson and Protenor
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X and Y Chromosomes Early Studies
Wilson and Lygaeus
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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
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Chromosome Composition in Humans
Karyotype