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Reproduction > Sexual Differentiation and DSDs > Flashcards

Sexual Differentiation and DSDs Flashcards

1
Q

What structures form from the paramesonephric ducts?

A

Uterus, oviducts, cervix and cranial vagina

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2
Q

What structures develop from the mesonephric ducts?

A

Epididymus and ductus deferens

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3
Q

What structures develop from the urogenital sinus?

A

The vestibule in females, and the urethra, prostate and bulbourethral glands in males

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4
Q

What factor determines whether testes or ovaries will develop?

A

Testes determining factor (TDF)

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5
Q

What hormone is produced by Sertoli cells?

A

Anti-Mullerian Hormone (AMH)

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6
Q

What is the function of AMH?

A

Its presence causes degeneration of the paramesonephric ducts, and leydig cells to differentiate. Its absence allows the paramesonephric ducts to form the oviducts, uterus and cranial vagina.

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7
Q

What is the function of dihydrotestosterone?

A

It causes development of penis, scrotum and accessory sex glands.

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8
Q

What is the function of testoserone in sexual development?

A

It causes the development of the male duct system

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9
Q

What are the three ways sex can be classified?

A
  1. Genotype/chromosomal sex
  2. Gonadal sex
  3. Phenotypic sex
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10
Q

What is genotype/chromosomal sex?

A
  • The chromosome constitution (XX or XY) and a balanced expression of a complex network of other genes drives the primitive gonaed to either follow the male differentiation pathway and suppress the female pathway or vice versa
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11
Q

What is gonadal sex?

A

Presence of testes or not (ovary)
- Genes and gene products drive gonadal and duct pathways
- Internal and external genitalia will follow the male pathway in presence of androgens and AMH, or the female pathway in their absence.

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12
Q

What is phenotypic sex?

A

Appearance of external genitalia, which is dependent on DHT (dihydrotestosterone) presence or absence.

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13
Q

During development the embryo uses three renal system. What are they?

A
  1. Pronephros= primary kidney, a non-functional remnant of the primitive kidney found in lower animals. REGRESSES COMPLETELY
  2. Mesonephros= intermediate kidney. The pronephros regresses and is replaced by these two bilateral kidneys. Urine is drained bilaterally by mesonephric duct/Wolffian duct.
  3. Metanephros= final kidney. By the first 10-15% of gestation the final form of the kidney appears. It will develop functional nephrons and becomes functional by the first 30-35% of gestation
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14
Q

Which form of embryonic kidney is “hijacked” by the reproductive system to form the gonads?

A

The mesonephros

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15
Q

What forms on either side of the mesonephric ducts while the embryo is still uncomitted to sex?

A

Paramesonephric/Mullerian ducts

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16
Q

ANY amount of presence of the SRY gene will result in continuation of the male pathway. T/F

A

FALSE- SRY levels need to reach a certain threshold at a certain stage of fetal development to induce testes development

17
Q

What is the main function of the SRY gene

A

It upregulates expression of the SOX9 gene in a very narrow critical window

18
Q

What are the main functions of the SOX9 gene?

A

It is a master regulator of testes determination and Sertoli cell formation, as well as downregulation of the FOXL2 gene (female)

19
Q

What is the main function of the SF1 gene?

A

It switches on the desert Hedgehog gene which results in differentiation of Leydig cells

20
Q

What is the function of 5 alpha reductase?

A

It converts testosterone into DHT within the Leydig cells

21
Q

Female is the default sex therefore the female pathway is passive. T/F

A

FALSE- while it may be the “default” it is still an ACTIVE process, we still need to ANTAGONISE the male pathway.

22
Q

What is the main function of the FOXL2 gene?

A

It maintains ovarian development

23
Q

What two female genes suppress SOX9?

A

DAX1 and WNT4

24
Q

Why don’t males have a surge centre in their hypothalamus?

A

Fetal males produce testosterone in the fetal testes, which crosses the B/B barrier, and is converted by aromatase into oestradiol, which “defeminises” the brain, casuing regression/decrease in function of the surge centre. Further presence of androgens as a neonate is required to cause complete regression. In females, the oestrogen produced is bound by fetal alphaprotein which makes the molecule to big to cross the B/B barrier, and the surge centre develops.

25
Q

What are the three main categories of DSD?

A
  1. Sex chromosome DSD- abnormalities of the sex chromosomes
  2. XX DSD- have normal female characteristics
  3. XY DSD- have normal male characteristics
26
Q

What will karyotyping tell us about a particular DSD?

A

It can tell us if something is wrong with the NUMBER of chromosomes

27
Q

What can a PCR test tell us about a particular DSD?

A

It can tell us if specific gene sequences are the problem

28
Q

What three things do we need to occur to get a freemartin?

A
  1. Dizygotic trwin pregnancy
  2. Fetuses of different sex
  3. Placental anastomosis-> sharing of blood supply between 2 placentas
29
Q

What is a freemartin?

A

A genetically female fetus that is masculinised in the presence of a male co-twin giving rise to a sterile heifer. This occurs in > 90% of dizygotic heterosexual twin pregnancies in cows

30
Q

Freemartins are chimeras. T/F

A

TRUE

31
Q

What do the gonads of a freemartin often look like?

A
32
Q

What does the repro tract of a freemartin often look like?

A
33
Q

What does the external genitalia of a freemartin often look like?

A
34
Q

How does XX/XY blood chimerism work in freemartinism?

A

There is sharing of blood across the placentas, so RBCs AND WBCs will be shared. These will be incorporated into the bone marrow, so the female will forever carry some XY in her blood?

35
Q

The presence of what hormone from the male co-twin causes disruption of sexual differentiation?

A

AMH

36
Q

Why do goats with PIS often have a limited uterus?

A

Cause the presence of AMH causes regression of the paramesonephric ducts.

Reproduction (10 decks)

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