Sexual Development Flashcards
Female Pseudohermaphrodite
XX w/ ovaries but male/ambiguous phentotype (less common than male pseudo)
Can occur in female puppies if mother is given too much progesterone during pregnancy
Urogenital Sinus (XX)
Remains open
Caudal vagina, vestibule
TDF
Testis determining factor (aka Sry protein, HY antigen)
Located on Y xsome
Anti-Müllerian Hormone (AMH)
Causes regression of female duct system (paramesonephric/Müllerian)
Produced by Sertoli cells (in male)
(Sometimes referred to as MIS)
X inactivation
Normal process in females!
Random X inactivation (leads to mosaicism, calico cats)
1 “X” in each cell is turned off (not the same “X” in all cells!)
Dihydrotestosterone
Product of testosterone and 5-alpha reductase
Potent androgen
Required for phenotypic masculinization (penis, scrotum, accessory glands)
Absence causes female differentiation
Mosaic
Animals w/ more than 1 genetically distant population of cells but all cells originate from a single zygote (non-disjunction during mitosis of early embryo)
Phenotype depends on proportion of normal cells
Ex. Tortoiseshell/calico cats (and debatably all normal females)
Abnormalities of Gonadal Sex
Xsomal & gonadal sex do not agree
Aka “sex reversal”
Ex: XY w/ ovaries, XX w/ testes
Primordial Germ Cells (PGCs)
Originate from yolk sac & migrate to genital ridge
Genital Swelling (XX)
Remains open
Vulva
Pseudohermaphrodite
Chromosomes and gonads agree but phenotype does not (ambiguity common)
Genital Ridge
Precursor of gonad
Undifferentiated, bipotential
Mesonephric/Wolffian Duct
Precursor to male reproductive organs (epididymis, deferent duct, urethra)
Present in early embryo alongside paramesonephric/Müllerian duct
Development promoted by testosterone
Genital Tubercle (XY)
Becomes penis (in presence of DHT)
Chromosomal Disorders of Sexual Differentiation
Originate from non-disjunction of sex xsomes or chromatids during meiosis/mitosis
Leydig Cells
Produce testosterone (development of mesonephric/Wolffian ducts into male repro organs)
Sex Reversed Males
XX w/ testes
Sry positive: Sry translocated onto X gene during meiosis
Sry negative: due to other mutations
Polled Intersex Syndrome (PIS)
Genes for polled condition and intersexuality on closely linked loci Intersex is recessive (PP female) , polled is dominant
PP female: degree of male differentiation, sterile
PP males: fertile
Pp: polled & fertile pp: horned & fertile (keep these males for safe breeding!!)
Phenotypic Sex
Determined by hormones produced by gonads
Masculinization: testosterone and DHT
Gonadal Sex (XY)
Initiated by functional Sry gene (TDF/HY Ag) on Y xsome
Testes develop
Kleinfelter’s Syndrome
Xsomal sex: XXY
Gonadal sex: testes (often cryptorchid)
Phenotypic sex: male (presence of Sry)
Usually sterile, abnormal phenotype (male calico cats)
Genital Tubercle (XX)
Becomes clitoris
True Hermaphrodite
Both ovarian AND testicular tissue present
- 1 testis, 1 ovary
- 1 testis, 1 ovotestis
- 1 ovary, 1 ovotestis
- 2 ovotestes
Genital Swelling (XY)
Closes (in presence of DHT)
Scrotum
Chromosomal Sex
Determined @ fertilization (XX or XY)
Drives gonadal differentiation
Male Pseudohermaphrodite
XY w/ testes but female/ambiguous phenotype (more common than female pseudo)
Trisomy X
Xsomal sex: XXX
Gonadal sex: ovaries
Phenotypic sex: female
Abnormal phenotype
Sex Reversed Females
Y xsome present, but w/ non-functional Sry gene
Undifferentiated/Streak gonads
Phenotype: female that is not fully developed
Sertoli Cells
Produce Anti-Müllerian Hormone (AMH)
Regression of paramesonephric/Müllerian duct system
Urogenital Sinus (XY)
Closes (in presence of DHT)
Urethra, prostate
Gonadal Sex (XX)
No Sry gene (TDF/HY Ag)
Wnt, Dax1, FoxL2 genes on both X’s
Ovaries develop
Paramesonephric/Müllerian Duct
Precursor to female reproductive organs (oviducts, uterus, cervix, cranial vagina)
Present in early embryo alongside mesonephric/Wolffian duct
Regresses in presence of AMH
Turner’s Syndrome/Monosomy
Xsomal sex: XO
Gonadal sex: ovary or streak gonad
Phenotypic sex: female
Small stature, underdeveloped internal & external genitalia, usually sterile
Freemartinism
Cow has a male/female set of twins
Twins placentas fuse, blood mixes
Female calf (freemartin) receives testosterone and DHT transplacentally from male before gonadal differentiation
Freemartin undergoes some masculinization and is sterile
Chimera
Animals w/ more than 1 genetically distinct population of cells and these cells originated from more than 1 zygote
Ex. freemartinism in bovine spp.
Abnormalities of Phenotypic Sex
Xsomal & gonadal sex do not agree w/ phenotypic sex (may be ambiguous)
Result of hormonal defect or hormone receptor defect
Ex. pseudohermaphrodites
