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Flashcards in Reproduction 1 Deck (58):
1

describe the determinants of sexual differation

The type of sex: genetic, genotypic, or chromosomal
determines

gonadal sex: ovaries+/-female fetal tract or testis+/-male fetal tract
determines

genital or phenotypic sex with external sexual characteristics - most importantly external genitalia from lower fetal tract development
determines????

gender identification

2

What are the characteristics of genetic/genotypic/chromosomal sex and how is it identified?

determined by sex chromosome endowment: XX, XY (especially the Y determined at fertilization)

Karyotyping

3

What are the characteristics of gonadal sex and how is it identified?

determined by normal differentiation and especially the activation of SRY/TDF to yield male at about 7 weeks and female at 11 weeks

histology of gonads

4

What are the characteristics of genital/phenotypic sex and how is it identified?

determined by the activation and integration of
1. neuroendocrine axes
2. paracrine, endocrine control of genital tract development

physical exam

5

What are the characteristics of gender identity?

independent of genotype, unknown

6

discuss the general male genetic identity

Y chromosome required for testicular development with rare exceptions

Sry - sex determining gene on Y chromosome
XY with no Sry develop ovaries
XX with added Sry develop testis
X chromosome encodes androgen receptor

7

discuss the general female genetic identity

Ovary development depends on XX and no Y

Loss of one X results in ovarian dysgenesis but no loss of female ducts or genitalia

8

When do primordial germ cells migrate to the gonadal ridge?

5-6 weeks of gestation

9

is the gonadal ridge male or female specific?

neither - it is indifferent

10

What are the gene factors that determine maleness?

Sry is a transcription factor for Sox9, which induces proliferation of the primitive sex cords

11

What are the gene factors that determine femaleness?

Rspo1 and Wnt4 drive developmental progression, but ovary development will occur regardless due to lack of Sry

12

What do female internal genitalia develop from?

the cortex of the gonadal ridge

13

What do male internal genitalia develop from?

the medulla of the gonadal ridge

14

What are the three structures of the indifferent duct system?

mesenephros
mullerian duct
wolffian duct

15

What is the function of the mesenephros

produces urine during 6-10 weeks gestation and acts as a transient kidney for the developing fetus

16

What induces the regression of the mullerian duct in males?

AMH and inhibin B made by sertoli cellls

17

What stimulates the formation of internal genitalia in males?

Testosterone and DHT - androgens formed by Leydig cells

18

What induces the regression of the wolffian duct in females?

absence of testis, not the presence of ovaries!

19

What does the mullerian duct differentiate into in females?

top: fallopian tubes
middle: uterus
bottom: cervix and upper third of vagina

20

What does the genital tubercle develop into?

males: glans penis

females: clitoris

21

what doe the urogenital folds develop into?

males: ventral penis

females: labia minora

22

What does the urogenital sinus develop into?

males: prostate

females: lower vagina

23

What do the labioscrotal folds develop into?

males: scrotum

females: labia majora

24

What do the penis, scrotum, and prostate require?

The conversion of testosterone into DHT

25

What causes developmental defects in male external genitalia?

inhibition or mutation in converting enzyme 5-alpha-reductase

26

What are some general features of mitosis?

somatic cells only. daughter cells are genetically identical

27

What are some general features of meiosis I?

germ cells, duplication of DNA, recombination of chromes = genetic diversity. Chromosomes split in meiosis I

28

What are some general features of meiosis II?

no duplication, chromatids split, 4 daughter cells

29

What are the three main cell types in the testes?

gametes: sperm
sertoli cells: secrete AMH and inhibin B
Leydig cells: synthesize and secrete testosterone/DHT

30

What are the cell types of the ovaries?

Gametes (ova) and follicular cells are the follicles

31

What does follicular maturation result in?

Granulosa cells – secrete and synthesize estrogens and progesterone

Thecal cells – make androgens

32

What does DHT stimulate development of?

prostate and external genitalia

33

What does testosterone stimulate development of?

male internal genitalia

34

What does the wolffian duct differentiate into in males?

top: epididymus
middle: ductus deferens
bottom: seminal gland, ejaculatory duct

35

What is unique about Meiosis I in females?

arrested at diplotene of prophase until activation (puberty to 45+ years)

36

What causes meiosis arrest, and what produces it?

Oocyte maturation inhibitor (OMI), secreted by follicular cells in ovary

37

what is unique about meiosis II in females?

arrested at metaphase II until fertilized by sperm

38

discuss spermatogenesis in males

ongoing process from puberty through old age

39

discuss some structural errors that can result in chromosome abnormalities?

translocations: equal or unequal exchange of chromosomal material

inversions: piece of chromosome gets inserted upside down

deletions/duplications: loss or addition of part of a chromosome

rings: two ends of chromosomes attached to form a ring

40

what can happen if part of the Y chromosome containing the Sry gene gets translocated to the X?

XX female with male phenotype due to presence of Sry gene - this happens because X is inactivated

XY with female phenotype due to lack of Sry gene

41

What is the genotype of Turner's Syndrome?

XO

42

What is the genotype of Klinefelter's Syndrome?

XXY

43

What is Klinefelter's Syndrome usually a result of?

meitotic non-disjunction

44

What is Turner's Syndrome characterized by?

Gonadal dysgenesis - ovaries do not develop and become a streak of fibrous tissue

Although one X becomes inactivated later in life, and thus only one is necessary for life, at this stage you must have both Xs for ovary development

45

Discuss some physical presentations of a person with Turner Syndrome

Short statue, shield chest, webbed neck, upper torso deformities. Most do not go through puberty or have menstrual cycles

46

Discuss some physical and hormonal traits of someone with Klinefelter's Syndrome

Patients have a Y chromosome - testes are present but are small and hyalinated, and they are infertile

Testosterone is low due to testicular dysfunction

Gynecomastia: elevated estradiol

micropenis, eunuchoid body: lower body > than upper body by at least 2" with short arms

47

What is the genetic etiology of hermaphroditism?

60% XX
20% XY
20% mosaicism/chimerism

48

What is the phenotype of hermaphroditism?

male/female designation is based on which gonad is present (internal or external for males)

49

What is male pseudohermaphroditism?

Testes present, but some or all female internal/external genitalia also present

50

What is an example of male pseudohermaphroditism?

Androgen resistance due to loss (complete) or mutation (partial) in X-linked androgen receptor gene (karyotype 46, XY)

51

discuss the hormonal and phenotypic traits of male pseudohermaphroditism due to complete androgen resistance

Y chromosome induces mullerian duct regression and testes (undescended)

lack of androgen effects (no Wolffian duct development, no external genitalia)

hormones: androgen levels are high due to lack of feedback, high estrogens lead to development of female body characteristics

phenotype: female with blind vaginal pouch

52

discuss the hormonal and phenotypic traits of male pseudohermaphroditism due to partial androgen resistance

Y chromosome induces mullerian duct regression and testes (undescended)

Wolffian duct develops, gynecomastia

hormones: Androgen levels are high due to lack of feedback, estrogen levels high (for male)

phenotype: ambiguous with blind vaginal pouch (under masculinized)

53

What is female pseudohermaphroditism?

Ovaries present, but some or all male internal/external
genitalia also present

54

female pseudohermaphroditism is a result of what?

Developmental defect – not due to chromosomal abnormality

55

What is the phenotype of female pseudohermaphroditism?

Virilization due to increased androgens. Ambiguous genitalia, advanced skeletal age

56

What are some examples of female pseudohermaphroditism?

Fetal congenital adrenal hyperplasia ** most common

Maternal androgen excess due to adrenal or ovarian tumors, possibly also due to progestational drugs (birth control)

57

what is "true" hermaphroditism?

Both testes and ovaries present “gonadal” sex, but phenotypic sex ambiguous (XX hermaphrodites typically raised as females)

Cryptorchidism (undescended testes) and hypospadias are common

No spermatogenesis because other Y genes not present

58

what might be a cause of true hermaphroditism?

Possible SRY translocation or loss of RSPO1 gene (testes repressor)