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Reproduction > Sex Determination > Flashcards

Sex Determination Flashcards

1
Q

3 stages of sexual differentiation

A

chromosome (XX, XY)
Gonadal (testes or ovaries)
Phenotypic (male or female characteristics)

each stage depends on previous

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2
Q

Male differentiation

A

Sex determining region (SRY protein/ TDF)
testes develop
sertoli cells secrete anti mullerian hormone (AMH)

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3
Q

Male differentiation, affects of sertoli cells

A

AMH causes leading cells to differentiate- produce testosterone (male duct system develops) or produce dihydrotestosterone ( penis, scrotum and access. sex glands develop)

Also cause degeneration of paramesonephric ducts

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4
Q

Female differentiation

A

specific genes on X chromosome cause ovaries to develop
no AMH
paramesonephric ducts become oviduct, uterus and part of vagina
complete female report tract

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5
Q

chromosomal sex

A

depends on sex chromosomes which are determined at time of fertilization

drives gonadal differentiation

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6
Q

gonadal and phenotypic sex

A

early stages are the same for both male and females

begin with undifferentiated precursor

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7
Q

precursor of gonad

A

gonadal ridge- swelling of body cavity and peritoneum

gonadal ridge= undifferentiated, biopotential, located next to mesonephros and mesonephric ducts

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8
Q

gametes

A

primordial germ cells- originate from yolk sac and migrate to the gonadal ridge

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9
Q

embryo proper

A

advanced embryo, not yet a fetus

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10
Q

gamete formation

A

yolk sac will decrease and allantois will increase in size

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11
Q

mesonephros

A

part of male reproductive system (duct)

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12
Q

paramesonephric duct

A

tubular system in females

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13
Q

gonadal ridge

A

precursor to gonad

primitive germ cells orginate in yolk sac and migrate to the gonadal ridge- organize into primitive sex cords

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14
Q

testis differentiation

A

Sry gene on sex determining region Y (and others on Y chromosome)

SRY protein (TDF-testis determining factor) initiates male sex determination

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15
Q

Ovarian differentiation

A

not default, requires two copies of key genes (Wnt4, Dax1, and FoxL2)

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16
Q

sex cords, testis differentiation

A

give rise to seminiferous tubules

sertoli cells- AMH, PGC give rise to spermatozoa eventually

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17
Q

Gonadal ridge, testis differentiation

A

leydig cells- testosterone

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18
Q

Ovarian development

A

absences of Sry and presence of other genes
sex cords regress
PGCs within follicles, on the surface of the ovary
PGCs give rise to oocytes
support and hormone producing cells- theca cells, granulosa cells

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19
Q

Tubular tract

A

both ducts present-Mesonephric (wolffian) and paramesonephric (Mullerian)

development depends on presence or absence of testicular hormones

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20
Q

Leydig cells

A

testosterone which is essential for development of mesonephric ducts

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21
Q

Sertoli cells

A

Anti Mullerian Hormones (AMH)

causes regression of the female (paramesonephric duct system)

22
Q

mesonephrons

A

primitive kidney, if male orange tube regresses

23
Q

Mesonephric/Wolffian ducts

A

epididymis, deferent ducts and urethran

24
Q

Paramesonephric/Mullerian ducts

A

Oviducts, uterus, cervix and cranial vagina

25
Q

Phenotypic sex

A

determined by hormones produced by gonad

Male: Testosterone and Dihydrotestosterone(DHT)
DHT= metabolite of testosterone- potent androgen

26
Q

Genital tubercle

A

in presence of DHT develops into penis and in absence into clitoris

27
Q

Genital swellings

A

DHT, develops into scrotum without into vulva

28
Q

Genital Folds

A

DHT, folds close/fuse and in absence folds do not fuse

29
Q

Disorders of Sexual Differentiation

A

can occur at any point in development

chromosomal, gonadal and phenotypic

30
Q

Chromosomal disorders of sexual differentiation

A

usually originate from non disjunction of sex chromosomes or chromatids during meiosis or mitosis

31
Q

nondisjunction

A

failure to separate chromosomes

32
Q

Monosomy X

A

X0 chromosomal sex

tuners syndrome- gonadal sex= ovary or streak gonad
phenotypic sex is female
small statue
usually underdeveloped internal and external genitalia due to lack of 2nd X chromosome

usually sterile

33
Q

Klinefelter’s Syndrome

A

XXY chromosomal sex
gonadal sex typically testes, often cryptorchid and phenotypically male

male due to presence of SRY

extra X chromosome leads to abnormal phenotype and usually sterile

common in ruminants

34
Q

Trisomy X

A

chromosomal XXX
gonadal sex is ovaries and phenotypic sex= female

usually abnormal phenotype due to presence of extra X

35
Q

Mosaics and chimeras

A

animals with more than one genetically distinct population of cells

36
Q

Mosaic

A

all cells originate from single zygote

usually results from non disjunction during mitosis of early embryo

37
Q

mosaic phenotype

A

depends on proportion of normal cells

large number of affected cells= embryonic death and most surviving Turners syndrome are mosaics

38
Q

Chimera

A

contain cell lines originating from two diff. embryonic sources

experimentally or naturally occurring

Ex: geep, sheep and goat embryo fused

39
Q

Freemartins

A

Chimera, most common in bovine

calf contains a portion of cells originating from its twin and is only clinically relevant when one is a male and other female

male and female characteristics with female tract underdeveloped

40
Q

how to get a chimera

A

placenta from twin bovine pregnancies fuse and blood from the two fetuses mix

placental fusion occurs before gonadal differentiation and hormones are transferred between fetuses

T and DHT from male masculinize the female fetus to varying degrees

41
Q

abnormalities of gonadal sex

A

occur when chromosomal sex and gonadal sex do not agree (SRY absent or nonfunctional)

sex reversals- XY sex reversed female so and XY with ovaries and an XX sex reversed male an XX with testes

42
Q

sex reversed females

A

Y chromosome present but SRY non-functional

gonads often undifferentiated (streak gonads), phenotype female but not fully developed

43
Q

sex reversed males

A

XX with testes

SRY positive, Sry translocated during crossing over (meiosis), differentiation proceeds in male direction due to functional SRY

SRY negative, mutation in gene downstream of SRY

44
Q

Abnormalities of phenotypic sex

A

something not turned on or off, when chromosomal sex and gonadal sex do not agree with phenotypic sex, or phenotype is ambiguous

XX with ovaries, male or ambiguous; XY with testes, female or ambiguous phenotype

usually resulting from hormonal defect or hormone receptor defect

45
Q

Testicular feminization

A

XY with testes, faulty androgen receptor

T and DHT cannot bind/exert effort which can affect testicular descent, formation of male tubular tract, external genitalia etc.

phenotype varies depending on severity of defect in receptor (vagina may be blind-ended, uterus hypo plastic, testes retained)

46
Q

5-a-reductase deficiency

A

XY with testes but reduced ability to convert testosterone to DHT

testosterone level is high, external genitalia develop as female and underdeveloped mesonephric (wolffish) duct

47
Q

Male pseudohermaphrodite

A

XY with testes, but female phenotype

48
Q

Female Pseudohermaphrodite

A

XX with ovaries but male phenotype

much less common

49
Q

ambiguous phenotype

A

have testes with female report organs finished

50
Q

True hermaphrodite

A

both ovarian and testicular tissue present, 1 testes and 1 ovary

usually gonadal errors

1 testes with 1 ovotestis
1 ovary with 1 ovotestis
2 ovotestes

Reproduction (22 decks)

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