Sexual Development

Question 1

Female Pseudohermaphrodite

Answer 1

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

Question 2

Urogenital Sinus (XX)

Answer 2

Remains open

Caudal vagina, vestibule

Question 3

TDF

Answer 3

Testis determining factor (aka Sry protein, HY antigen)

Located on Y xsome

Question 3

Anti-Müllerian Hormone (AMH)

Answer 3

Causes regression of female duct system (paramesonephric/Müllerian)

Produced by Sertoli cells (in male)

(Sometimes referred to as MIS)

Question 4

X inactivation

Answer 4

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!)

Question 5

Dihydrotestosterone

Answer 5

Product of testosterone and 5-alpha reductase

Potent androgen

Required for phenotypic masculinization (penis, scrotum, accessory glands)

Absence causes female differentiation

Question 5

Mosaic

Answer 5

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)

Question 6

Abnormalities of Gonadal Sex

Answer 6

Xsomal & gonadal sex do not agree

Aka “sex reversal”

Ex: XY w/ ovaries, XX w/ testes

Question 7

Primordial Germ Cells (PGCs)

Answer 7

Originate from yolk sac & migrate to genital ridge

Question 8

Genital Swelling (XX)

Answer 8

Remains open

Vulva

Question 8

Pseudohermaphrodite

Answer 8

Chromosomes and gonads agree but phenotype does not (ambiguity common)

Question 9

Genital Ridge

Answer 9

Precursor of gonad

Undifferentiated, bipotential

Question 10

Mesonephric/Wolffian Duct

Answer 10

Precursor to male reproductive organs (epididymis, deferent duct, urethra)

Present in early embryo alongside paramesonephric/Müllerian duct

Development promoted by testosterone

Question 10

Genital Tubercle (XY)

Answer 10

Becomes penis (in presence of DHT)

Question 11

Chromosomal Disorders of Sexual Differentiation

Answer 11

Originate from non-disjunction of sex xsomes or chromatids during meiosis/mitosis

Question 13

Leydig Cells

Answer 13

Produce testosterone (development of mesonephric/Wolffian ducts into male repro organs)

Question 14

Sex Reversed Males

Answer 14

XX w/ testes

Sry positive: Sry translocated onto X gene during meiosis

Sry negative: due to other mutations

Question 14

Polled Intersex Syndrome (PIS)

Answer 14

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!!)

Question 16

Phenotypic Sex

Answer 16

Determined by hormones produced by gonads

Masculinization: testosterone and DHT

Question 17

Gonadal Sex (XY)

Answer 17

Initiated by functional Sry gene (TDF/HY Ag) on Y xsome

Testes develop

Question 18

Kleinfelter’s Syndrome

Answer 18

Xsomal sex: XXY

Gonadal sex: testes (often cryptorchid)

Phenotypic sex: male (presence of Sry)

Usually sterile, abnormal phenotype (male calico cats)

Question 20

Genital Tubercle (XX)

Answer 20

Becomes clitoris

Question 22

True Hermaphrodite

Answer 22

Both ovarian AND testicular tissue present

• 1 testis, 1 ovary
• 1 testis, 1 ovotestis
• 1 ovary, 1 ovotestis
• 2 ovotestes

Question 23

Genital Swelling (XY)

Answer 23

Closes (in presence of DHT)

Scrotum

Question 24

Chromosomal Sex

Answer 24

Determined @ fertilization (XX or XY) Drives gonadal differentiation

Question 25

Male Pseudohermaphrodite

Answer 25

XY w/ testes but female/ambiguous phenotype (more common than female pseudo)

Question 26

Trisomy X

Answer 26

Xsomal sex: XXX Gonadal sex: ovaries Phenotypic sex: female Abnormal phenotype

Question 26

Sex Reversed Females

Answer 26

Y xsome present, but w/ non-functional Sry gene Undifferentiated/Streak gonads Phenotype: female that is not fully developed

Question 27

Sertoli Cells

Answer 27

Produce Anti-Müllerian Hormone (AMH) Regression of paramesonephric/Müllerian duct system

Question 28

Urogenital Sinus (XY)

Answer 28

Closes (in presence of DHT) Urethra, prostate

Question 30

Gonadal Sex (XX)

Answer 30

No Sry gene (TDF/HY Ag) Wnt, Dax1, FoxL2 genes on both X's Ovaries develop

Question 31

Paramesonephric/Müllerian Duct

Answer 31

Precursor to female reproductive organs (oviducts, uterus, cervix, cranial vagina) Present in early embryo alongside mesonephric/Wolffian duct Regresses in presence of AMH

Question 32

Turner's Syndrome/Monosomy

Answer 32

Xsomal sex: XO Gonadal sex: ovary or streak gonad Phenotypic sex: female Small stature, underdeveloped internal & external genitalia, usually sterile

Question 33

Freemartinism

Answer 33

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

Question 35

Chimera

Answer 35

Animals w/ more than 1 genetically distinct population of cells and these cells originated from more than 1 zygote Ex. freemartinism in bovine spp.

Question 36

Abnormalities of Phenotypic Sex

Answer 36

Xsomal & gonadal sex do not agree w/ phenotypic sex (may be ambiguous) Result of hormonal defect or hormone receptor defect Ex. pseudohermaphrodites