Sex Determination Outline
Sex Determination and Development
Page 1: Introduction
Overview of sex determination and development.
Page 2: Objectives of Lecture
Understand the transcription factors and hormones involved in sex determination.
Explore how temperature affects gene expression and enzymes which result in male or female outcomes.
Examine how chromosomal, gonadal, reproductive tract, and brain sex contribute to different phenotypic characteristics and fertility.
Understand the evolutionary conservation of sex determination in amphibians, avians, and mammalian species.
Discuss how inappropriate regulation of transcription factors, hormones, and temperature may affect sex determination.
Recognize exceptions in mammalian sex determination and development.
Page 3: Evolutionary Conservation of Embryonic Development
Embryonic development stages across species: Fish, Tortoise, Chick, Pig, Calf, Rabbit, Human, Salamander.
Page 4: Chromosomal Sex Determination
Chromosomal Sex:
Males: XY
Females: XX
Gonadal Sex:
Males: Testis
Females: Ovary
Phenotypic Sex:
Traits such as voice, breasts, fat deposition, hair patterns, and other characteristics.
Behavioral Sex: Sex of the brain in mammals.
Page 5: Recombination of Sex Chromosomes at Fertilization
Chromosomal Sex (Genotype):
Mammals: Male = XY, Female = XX
Birds: Male = ZZ, Female = ZW
Some reptiles have temperature-dependent sex determination.
In female mammals, one X chromosome is inactivated (Barr body).
Abnormalities:
XXY: Klinefelter’s syndrome - sterile, testicular hypoplasia.
XO: Turner’s syndrome - sterile, inactive ovaries.
Page 6: Gene Expression and Gonadal Differentiation
Key genes for gonadal differentiation: Gata4/Fog2, Sry, Sox9, Fgf9/Fgfr2.
Role of Sox9 in maintaining Sertoli cell fate in XY gonads and downregulation in XX gonads.
FOXL2 expression begins before its function is critical in ovarian development.
Page 7: Temperature and Gonadal Development in Turtles
Development stages and temperatures affecting sex determination in freshwater and marine turtles (Emys orbicularis and Dermochelys coriacea).
Key terms: thermosensitive period, hatching, testicular differentiation, ovarian differentiation.
Page 8: Gonadal Stages in Turtles
Distinction of stages in indifferent gonads and their temperature sensitivity at various developmental stages.
Page 9: Molecular Events in Gonadal Development
Hormonal and physiological events in differentiation into gonads in response to temperatures.
Page 10: Sex Determination Gene: Sry
Sry Gene:
Located on the Y chromosome, crucial for male development.
Stimulates seminiferous cord formation in testes.
Useful for embryo sexing.
Page 11: Reverse Transcription - PCR Applications
Applications of RT-PCR in different species including human, horse, dog, mice, cattle, sheep.
Page 12: Overview of Gonadal Differentiation
Early mouse sex differentiation flow including genes involved in testicular and ovarian development (Sry, Sox9, etc.).
Importance of timing in the expression of sex determination genes.
Page 13: Gonadal Differentiation Overview
Continued developments of female and male reproductive systems.
Page 14: Female Reproductive Anatomy
Anatomy of the female reproductive tract including ovary, oviduct, uterus, bladder, vagina.
Page 15: Male Reproductive Anatomy
Anatomy of the male reproductive tract including testes, epididymis, bladder, vas deferens, seminal vesicle, prostate, Cowper's gland.
Page 16: Formation of Male and Female Reproductive Systems
Pathway leading to male and female reproductive systems based on presence or absence of testis-determining factor (TDF) and hormones such as AMH, testosterone, and dihydrotestosterone.
Page 17: Differentiation of Gonads
Migration of primordial germ cells to mesonephros influences gonadal differentiation.
Page 18: Developmental Stages of the Embryo
Key embryonic structures involved in reproductive development including genital ridge and mesonephric ducts.
Page 19: Indifferent Gonads
Morphological changes during gonadal differentiation and the roles of Wolffian and Müllerian ducts.
Page 20: Morphological Changes
Detailed morphological changes during sex differentiation in fetal testis and ovary development.
Page 21: Events During Sex Determination
Detailed timeline of events during the first, second, and third trimester of sexual differentiation including germ cell migration and differentiation of external and internal genitalia.
Page 22: Development of Reproductive Tract and External Genitalia
Formation of female and male tracts from the Müllerian and Wolffian ducts respectively.
Page 23: Hormonal Production in the Male Gonad
Production of hormones including Müllerian Inhibiting Hormone and androgens that are crucial for male reproductive tract development.
Page 24: Testosterone Metabolism Routes
Possible metabolic pathways of testosterone in developing tissues, including conversion and functions.
Page 25: General Overview of Reproductive Structures
Description of undifferentiated reproductive structures in developing embryos.
Page 26: Continued Development Stages
Further stages of development within undifferentiated external reproductive structures in males and females.
Page 27: Reproductive Development Continued
Overview of further stages and structures in reproductive anatomy development.
Page 28: Differentiation of External Genitalia
Overview of differentiation processes of external genitalia in both sexes and key structures involved.
Page 29: Testis Descent
Anatomical overview and processes related to the descent of testes in males.
Page 30: Hermaphroditism
Types of hermaphroditism and congenital malformations in sexual development.
Page 31: Gene Defects in Men
Overview of variants like 5a reductase deficiency and congenital adrenal hyperplasia affecting male sexual development.
Page 32: 21-Hydroxylase Deficiency in CAH
Pathways involved in congenital adrenal hyperplasia leading to variations in sexual development.
Page 33: Abnormal Female Development
Overview of conditions like hermaphroditism in swine and abnormal reproductive tract formations.
Page 34: Freemartin Conditions in Bovine
Analysis of abnormal female development in bovine twins fused at the placenta.
Page 35: Bovine Twin Fusion
Specific cases of congenital issues arising from placenta fusion in bovine.
Page 36: Sexual Differentiation of the Brain
Role of testicular hormones, aromatization and a-fetoprotein in sexual differentiation of the brain.
Page 37: Blood Brain Barrier and Hormonal Interaction
The effects of a-fetoprotein on estrogen in females vs. the free penetration of testosterone in males.
Page 38: Control Centers in Reproductive Physiology
Overview of control centers for reproductive hormone secretion in the brain.
Page 39: Testosterone Metabolism in the Brain
Different metabolic routes that testosterone can take within the developing brain tissue.
Page 40: Brain Sexual Dimorphism
Highlighted structures in male and female brains and their implications for sexual differentiation.
Page 41: Behavioral Differences in Rams
Behavioral differences observed between female-oriented and male-oriented rams, related to their sexual orientation preferences.
Page 42: oSDN Differences
Graphical representation of behavioral research findings on sexual dimorphism in rams.
Page 43: Behavioral Tests Results
Summary of behavior exhibited by female-oriented vs male-oriented rams in tests involving estrous ewes and rams.
Page 44: Aromatase Investigation Results
Measurement results comparing aromatase mRNA expression among different groups of rams and ewes.
Page 45: Exceptions to the Rules
Examples of three mammals (spotted hyenas, elephants, tammar wallabies) where sexual differentiation follows unconventional patterns.
Page 46: Spotted Hyena Behavior
Description of social behaviors and mating presentations in spotted hyenas.
Page 47: Elephant Copulating Behavior
Overview of copulation capabilities and anatomical differentials between male and female elephants.
Page 48: Tammar Wallaby Development Stages
Visual and descriptive understanding of developmental stages in tammar wallabies indicating indeterminate phases.