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Sex Determination Chromosomal Sex Determination

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Presentation on theme: "Sex Determination Chromosomal Sex Determination"— 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? Sox9 Chromosomes: XX Bipotential Gonad Wnt4, R-spo1
b-catenin Sox9 Ovary

9 Boy or Girl? Sox9 Chromosomes: XY Anti Mullerian Factor (AMF)
Bipotential Gonad Anti Mullerian Factor (AMF) Fgf9 Sf1 Sry, Sf1 Testes Sox9 b-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
Caster Semenya Hermaphrodites: Having secondary sex characteristics for both genders Androgen Insensitivity Syndrome Chromosomal Translocation of SRY Pseudohermaphroditism Congenital Adrenal Hyperplasia

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 a-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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