Human Development – Lecture 17 – Genetics and inheritance
Chromosomal abnormalities;
13 (Patau, early death), 18 (Edward, early death), 21 (Down, nondisjunction) and 22.
Trisomy 9 is embryonic lethal.
XXY → Klinefelter
XYY → Jacobs
XXX → triple X
X0 → Turner
Sex determination;
2 kinds of sex determination;
1. Genotypic sex (XX or XY)
2. Environmental sex
• gonade (geschlachtsklier)
• phenotypic (geslachtsorgaan) (internal & external genitalia))
Sex;
• Genetic → chromosomes; these determine gonadal seks & internal
genitals. The system starts bisexual. Only one (mostly) survives.
• Gonadal → gonads
• Genitals → internal & external
Gender; social meaning attached to being male or female.
Physicians have recommended that intersex people be reared as girls.
Male development;
1. Genetic factors initiate processes that directs the indifferent gonads toward
testis development
2. Activation Sertoli cells to produce Mullerian inhibiting hormone
3. Activation Leydig cells to secrete testosterone; development of Wolffian ducts
toward epidydimes, vas deferens and seminal vesicles. (internal structure)
Testosterone → dihydrotestosterone (DHT); development of urethra, prostate
gland and penis. (external structures)
Testosterone in blood; organs; hair, muscle, brain, testes, sex accessory
DHT in the target organ; behavior and reproduction; aggression, libido,
spermatogenesis, external genitalia
Y-chromosome (short chromosome)(recombine with itself)
• Produce testis determination factor (TDF) =SRY
• SRY activated Sertoli and Leydig
• Acts together with autosome gene SOX9
• SOX9 bind to promotor of MIH (or AMH) and regulates its expression.
• SRY/SOX9 induce FGF9 → penetrate (doordringen) gonadal ridge (without no
testis can be formed)
• Steroidogeneis factor 1; stimulates differentiation of Sertoli & Leydig cells
• SF1 stimulates Leydig cells to make enzymes for testosterone production.
Chromosomal abnormalities;
13 (Patau, early death), 18 (Edward, early death), 21 (Down, nondisjunction) and 22.
Trisomy 9 is embryonic lethal.
XXY → Klinefelter
XYY → Jacobs
XXX → triple X
X0 → Turner
Sex determination;
2 kinds of sex determination;
1. Genotypic sex (XX or XY)
2. Environmental sex
• gonade (geschlachtsklier)
• phenotypic (geslachtsorgaan) (internal & external genitalia))
Sex;
• Genetic → chromosomes; these determine gonadal seks & internal
genitals. The system starts bisexual. Only one (mostly) survives.
• Gonadal → gonads
• Genitals → internal & external
Gender; social meaning attached to being male or female.
Physicians have recommended that intersex people be reared as girls.
Male development;
1. Genetic factors initiate processes that directs the indifferent gonads toward
testis development
2. Activation Sertoli cells to produce Mullerian inhibiting hormone
3. Activation Leydig cells to secrete testosterone; development of Wolffian ducts
toward epidydimes, vas deferens and seminal vesicles. (internal structure)
Testosterone → dihydrotestosterone (DHT); development of urethra, prostate
gland and penis. (external structures)
Testosterone in blood; organs; hair, muscle, brain, testes, sex accessory
DHT in the target organ; behavior and reproduction; aggression, libido,
spermatogenesis, external genitalia
Y-chromosome (short chromosome)(recombine with itself)
• Produce testis determination factor (TDF) =SRY
• SRY activated Sertoli and Leydig
• Acts together with autosome gene SOX9
• SOX9 bind to promotor of MIH (or AMH) and regulates its expression.
• SRY/SOX9 induce FGF9 → penetrate (doordringen) gonadal ridge (without no
testis can be formed)
• Steroidogeneis factor 1; stimulates differentiation of Sertoli & Leydig cells
• SF1 stimulates Leydig cells to make enzymes for testosterone production.
