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Sex Determination Chromosomal Sex Determination Primary and Secondary Sex Determination Another model of chromosomal sex determination: Drosophila Environmental.

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Presentation on theme: "Sex Determination Chromosomal Sex Determination Primary and Secondary Sex Determination Another model of chromosomal sex determination: Drosophila Environmental."— Presentation transcript:

1 Sex Determination Chromosomal Sex Determination Primary and Secondary Sex Determination Another model of chromosomal sex determination: Drosophila Environmental Regulation of Sex Determination

2 Mammalian Sex Chromosomes Formation of bipotential gonad. Males= XY Females= XX Sex determined by Y chromosome- SRY gene

3 Bipotential Gonad Formation Intermediate Mesoderm Mesonephric tubules

4 Bipotential Gonad Formation Intermediate Mesoderm Mesonephric tubules WT1 Wnt4 SF1 Sox9 FGF9 GATA4

5 Bipotential Gonad Formation Intermediate Mesoderm Mesonephric tubules Formation of Sex specific gonads

6 Bipotential Gonad Formation Intermediate Mesoderm Mesonephric tubules Formation of Sex specific gonads Reorganization of ducts Figure 14.3

7 SRY Gene Only on Y Chromosome Upregulates Sox9

8 Boy or Girl? Bipotential Gonad Ovary Sox9  -catenin Wnt4, R-spo1 Chromosomes: XX

9 Boy or Girl? Bipotential Gonad Sox9 Chromosomes: XY Sry, Sf1 Anti Mullerian Factor (AMF) Fgf9 Sf1 Testes  -catenin

10 Sox9: Autosomal Testis-determination gene

11 Secondary Sex Characteristics: Females Estrogen Fig. 14.3

12 Secondary Sex Characteristics

13 Male Phenotype: Testosterone and AMF AMF: blocks development of Müllerian Tube Testosterone and dihydrotestosterone

14 Genetics of Secondary Sex determination Hermaphrodites: Having secondary sex characteristics for both genders Androgen Insensitivity Syndrome Chromosomal Translocation of SRY Pseudohermaphroditism Congenital Adrenal Hyperplasia Caster Semenya

15 Sex on the Brain SRY and the brain Aromatase Gyandromorphs: Some body parts male, some female Bird Gyandromorphs

16 Sex on the Brain Most Mammals, estrogen (estradiol) masculinizes the brain  -Fetoprotein Prostaglandin E2 (PGE2)- growth of areas in male brain involved in sexual behavior (hypothalmus, limbic system)

17 Drosophila Sex Determination XX/XY Previously called X:A ratio Sex-Lethal (Sxl)

18 Sxl Dosage and Sex Determination

19 RNA splicing and Sex Determination

20 Fruitless: Mating Behavior

21 Environmental Sex Determination Temperature Location, Location, Location

22 Temperature and Reptiles

23 Temperature and Estrogen

24 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

25 Location


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