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Phenotypic Expression:

Phenotypic Expression:. Gene expression often governed by genotype and environment. *Penetrance. Example: if 9/10 of individuals carrying an allele express the trait, the trait is said to be 90% penetrant. *Expressivity. *Temperature. *Onset of genetic expression.

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Phenotypic Expression:

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  1. Phenotypic Expression: Gene expression often governed by genotype and environment *Penetrance Example: if 9/10 of individuals carrying an allele express the trait, the trait is said to be 90% penetrant *Expressivity *Temperature *Onset of genetic expression

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

  3. Chlamydomonas

  4. Maize (Zea mays)

  5. silkless (sk) tassel seed (ts) barren stalk (ba) Mutants of Maize

  6. Caenorhabditis elegans (C. elegans)

  7. Review: Sexual Differentiation Life cycles and reproductive modes *Asexual reproduction – C.elegans hermaphrodite vegetative Chlamydomonas *Sexual reproduction – Chlamydomonas C. elegans Maize Humans *Alternation in cycles - Chlamydomonas Maize

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

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

  10. 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

  11. XX Chromosome Composition in Humans Karyotype XY

  12. The Y Chromosome Pseudoautosomal regions (PAR) NRY Testis Determining Factor (TDF) *SRY – Sex determining region Is the Y chromosome a “genetic wasteland”? *Housekeeping genes *Testis development and function

  13. The Y Chromosome SKALETSKY, et al. (2003) The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature 423, 825 - 837

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