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Published byLewis Stafford Modified over 9 years ago
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Sex Determination Chromosomal Sex Determination
Primary and Secondary Sex Determination Another model of chromosomal sex determination: Drosophila Environmental Regulation of Sex Determination
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Mammalian Sex Chromosomes
Formation of bipotential gonad. Males= XY Females= XX Sex determined by Y chromosome- SRY gene
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Bipotential Gonad Formation
Intermediate Mesoderm Mesonephric tubules
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Bipotential Gonad Formation
Intermediate Mesoderm Mesonephric tubules WT1 Wnt4 SF1 Sox9 FGF9 GATA4
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Bipotential Gonad Formation
Intermediate Mesoderm Mesonephric tubules Formation of Sex specific gonads
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Bipotential Gonad Formation
Intermediate Mesoderm Mesonephric tubules Formation of Sex specific gonads Reorganization of ducts Figure 14.3
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SRY Gene Only on Y Chromosome Upregulates Sox9
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Boy or Girl? Sox9 Chromosomes: XX Bipotential Gonad Wnt4, R-spo1
b-catenin Sox9 Ovary
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Boy or Girl? Sox9 Chromosomes: XY Anti Mullerian Factor (AMF)
Bipotential Gonad Anti Mullerian Factor (AMF) Fgf9 Sf1 Sry, Sf1 Testes Sox9 b-catenin
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Sox9: Autosomal Testis-determination gene
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Secondary Sex Characteristics: Females
Estrogen Fig. 14.3
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Secondary Sex Characteristics
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Male Phenotype: Testosterone and AMF
AMF: blocks development of Müllerian Tube Testosterone and dihydrotestosterone
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Genetics of Secondary Sex determination
Caster Semenya Hermaphrodites: Having secondary sex characteristics for both genders Androgen Insensitivity Syndrome Chromosomal Translocation of SRY Pseudohermaphroditism Congenital Adrenal Hyperplasia
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Sex on the Brain SRY and the brain Aromatase
Gyandromorphs: Some body parts male, some female Bird Gyandromorphs
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Sex on the Brain Most Mammals, estrogen (estradiol) masculinizes the brain a-Fetoprotein Prostaglandin E2 (PGE2)-growth of areas in male brain involved in sexual behavior (hypothalmus, limbic system)
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Drosophila Sex Determination
XX/XY Previously called X:A ratio Sex-Lethal (Sxl)
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Sxl Dosage and Sex Determination
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RNA splicing and Sex Determination
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Fruitless: Mating Behavior
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Environmental Sex Determination
Temperature Location, Location, Location
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Temperature and Reptiles
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Temperature and Estrogen
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Environment and Sex Determination: Atrazine
Polychlorinated biphenyl compounds (PCBs) act as estrogens Atrazine: Weed killer As low as 0.1 ppb can have gonadal/sexual anomalies in male frogs. U.S. Drinking water= 3 ppb Midwestern water = ~224 ppb Hayes et al (2002) found that 7 of 8 sites in Midwest contain Atrazine. Atrazine upregulates Aromatase PCBs Atrazine
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Location
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