Sexuual Determination and DIfferentiation Flashcards
According to the Jost Paradigm, which of the following correctly represents the sequential determination of sex?
A. Gonadal sex → Genetic sex → Phenotypic sex
B. Phenotypic sex → Gonadal sex → Genetic sex
C. Genetic sex → Gonadal sex → Phenotypic sex
D. Genetic sex → Phenotypic sex → Gonadal sex
Genetic sex → Gonadal sex → Phenotypic sex
🧠 Rationale: The Jost Paradigm explains that genetic sex is determined at fertilization, which then directs the development of gonadal sex (testes or ovaries), which in turn influences phenotypic sex (internal and external genitalia)
.
Which combination best describes the three types of sex classifications in humans?
A. Genetic sex (autosomes), Gonadal sex (hormones), Genital sex (external appearance)
B. Genetic sex (chromosomes), Gonadal sex (gonads), Genital sex (genitalia)
C. Genetic sex (hormones), Gonadal sex (testosterone), Genital sex (gonads)
D. Genetic sex (enzymes), Gonadal sex (ovaries), Genital sex (internal hormones)
B. Genetic sex (chromosomes), Gonadal sex (gonads), Genital sex (genitalia)
🧠 Rationale: Genetic sex refers to chromosomal composition (XX or XY), gonadal sex refers to presence of testes or ovaries, and genital/phenotypic sex refers to internal and external genitalia
.
What chromosomal configuration leads to male sex determination at conception?
A. XX with a functional DAX1 gene
B. XY with a defective SRY gene
C. XY with a functional SRY gene
D. XO with SRY gene insertion
C. XY with a functional SRY gene
🧠 Rationale: The presence of a functional SRY gene on the Y chromosome triggers differentiation of bipotential gonads into testes. Without it, development defaults to female
.
Why does the absence of the Y chromosome lead to the development of ovaries by default?
A. Because the X chromosome directly stimulates ovarian formation through SRY gene expression
B. Because the lack of the SRY gene on the Y chromosome prevents testicular differentiation, allowing ovarian development by default
C. Because the absence of testosterone production from the X chromosome initiates ovarian differentiation
D. Because the Müllerian duct actively converts bipotential gonads into ovaries when Y chromosome is absent
B. Because the lack of the SRY gene on the Y chromosome prevents testicular differentiation, allowing ovarian development by default
🧠 Rationale: In the absence of the SRY gene—which is located on the Y chromosome—the bipotential gonads do not differentiate into testes, and as a result, ovarian development occurs by default without the need for active induction
.
What are the syndromes correlating to XXY and a lack of X chromosomes
XXY occurs in males and leads to Klinefelter’s syndrome (small testes, growth of breats tissue, widening of hips
Lack of X, occurs in females, leads to turners syndrome (causes streak and underdevelopment of ovaries)
Both condititions leads to infertility and lack of function in gonads
Which of the following is TRUE regarding Turner’s syndrome?
A. Individuals have functional ovaries and regular menstrual cycles due to the presence of two X chromosomes
B. Turner’s syndrome results in testicular development due to an SRY gene mutation
C. The condition leads to streak ovaries and absence of menstrual cycles due to missing or incomplete X chromosome
D. Individuals with Turner’s syndrome have normal fertility and complete internal female genitalia
C. The condition leads to streak ovaries and absence of menstrual cycles due to missing or incomplete X chromosome
🧠 Rationale: Turner’s syndrome is characterized by an XO karyotype (missing one X chromosome), leading to streak ovaries, lack of estrogen production, and primary amenorrhea (no menstrual cycles)
.
Which of the following correctly distinguishes male and female sexual differentiation during development?
A. Females require testosterone for Müllerian duct development
B. Males require MIH for Wolffian duct formation
C. Females develop internal genitalia due to absence of MIH and testosterone
D. Males develop ovaries in absence of DHT
Females develop internal genitalia due to absence of MIH and testosterone
🧠 Rationale: In females, absence of MIH allows Müllerian ducts to persist; lack of testosterone prevents Wolffian duct development. Differentiation happens by “default” in the female pathway
testosterone hleps for the development of wolffian ducts, not MIH
.
How does sexual differentiation differ in males and females? And what are the functions of the hormones?
Males:
- testes secrete MIH from sertoli cells, which inhibit growth of Mullerian ducts (which inhibits growth of female internal genitalia)
- testesterone from leydig cells, which cause development of male internal genitalia
-DHT (converted from testosterone and cause masculization of external male genitalia
Females:
- have no DHT, T and MIT
- growth of mullerian ducts for internal female genitalia
- female differentiation happens by default
Whats the difference between T and DHT
T issecreted by leydic cells ans is used for internal male genitalia development
DHT is converted form testosterone and causes masculinization of male externa;l genitalia
Which is true about males?
A. Development of wolffian ducts
B. Development of Mullerian ducts
Development of Wolffian ducts
Study trick
Men=Wolfian ducts
WOman= Mularein ducts
( the opposite of W and M is you get what i mean)
Which pairing of syndrome and chromosomal anomaly is accurate?
A. Klinefelter syndrome – XO
B. Turner syndrome – XXY
C. Klinefelter syndrome – XXY
D. Turner syndrome – XY
✅ Answer: C. Klinefelter syndrome – XXY
🧠 Rationale: Klinefelter syndrome results from an XXY configuration and affects male development; Turner syndrome results from XO, impairing ovarian development and fertility
.
What determines whether bipotential gonads develop into testes or ovaries during early embryonic development?
A. Presence of two X chromosomes activates SRY gene, triggering testis formation
B. Absence of SRY gene allows bipotential gonads to differentiate into testes by default
C. Presence or absence of the SRY gene directs bipotential gonads to develop into testes or ovaries, respectively
D. Gonads always develop into testes unless inhibited by estrogen from maternal circulation
Presence or absence of the SRY gene directs bipotential gonads to develop into testes or ovaries, respectively
🧠 Rationale: Bipotential gonads have the capacity to develop into either testes or ovaries. The presence of the SRY gene on the Y chromosome initiates testis development. In its absence, gonads default to ovarian development
.
What initiates the activation of the hypothalamic-pituitary-gonadal (HPG) axis during puberty?
A. Sudden drop in sex steroids
B. Increased sensitivity of GnRH receptors
C. Pulsatile release of GnRH from the hypothalamus
D. Continuous release of FSH and LH
C. Pulsatile release of GnRH from the hypothalamus
🧠 Rationale: Puberty onset begins with a pulsatile release of GnRH, which stimulates the pituitary to release FSH and LH, activating the gonads
A person with the XX chromosomes outwardly appears male, What is the cause of this?
The person has a mutation in the enzyme that makes cortisol. This slows down the enzymatic pathways of making cortisol.
As a result, there is a loss of negative feedback and increased cholesterol in the adrenal cortex
The extra cholesterol is used to increase androgens, and a hypersecretion of androgens leads to virilization (or masculization of EXTERNAL GENITALIA) which explains why they appear that way
A male with the XY chromosome appears to be female on the outside, what is the reason behind this?
The person has complete androgen insensitivity syndrome (CAIS)
They make MIH (no ovaries, fallopian tubes) and have T and DHT, BUT the androgens are unresponsive to T and DHT. The person has testes inside and female externa
This leads to the males having a female, like body and androgens are converted into estrogen in tissue
Which of the following is the cause of Complete androgwn insensitivity syndrome?
A. Mutation in the enzyme that makes cortisol
B. Mutation of MIH receptor
C. Mutation of androgen receptor
C. Mutation of the androgen receptor.
The androgen receptor having a mutation doesnt allow a person with XY chromosomes to have no development of male internal and external reproductive structures
They hae a female externa and the present of testes
What triggers the ONSET of puberty
Increased secretion of GnRh from the pulse generator, whichc causes the hypothalamus to increase LH and FSH and stimulates the anterior pituirary to increase sex steroid which act on the gonads, which then cause changes in puberty
How do hormone levels differ in the hypothalamic-pituitary-gonafal axis in a prepubertal child and at the time of puberty?
Prepubertal child:
- there is a very sensitive negative feed back to the hypothalamus due to low sex steroids
-low GnRh-low LH and FSH-then low sex steroids
At the time of puberty:
- KISSPEPTIN (neuropeptide) stimulates the hypothalamus to release lots of GnRH
- this causes more LH and FSH and more sex steroid hormones, leading to puberty
What are two factors that cause the increase of GnRh, potentially leading to puberty?
Leptin (in adipose tissue) and Kisspeptin
Note, people with more body fat start puberty earlier
Do more sex steroid cause negative or positive feedback to the hypothalamus
A term used to describe irregular cycles or absence of cycles
What is climacteric?
A decline in endocrine, somatic, reproductic and physiological functions
In males: andropause
In females: menopause
Which hormonal change characterizes the onset of menopause?
A. Decrease in GnRH and increase in estrogen
B. Increase in FSH and LH due to ovarian failure
C. Surge in progesterone and inhibition of FSH
D. Low FSH and high inhibin B levels
✅ Answer: B. Increase in FSH and LH due to ovarian failure
🧠 the loss of the ovarian cycle is due to a loss of negative feedback, causing high levels of estrogen to go up
.
What is the reason to many side effects of menopause
Negative side affects is due to the decrease of estrogen (mainly)
Also there is decreased progesterone due to no more corpus luteum
