Sexual Differentiation: How to Make a Boy or a Girl Flashcards
1
Q
Prevalence of genital abnormalities is 1 in ….
A
Prevalence of genital abnormalities is 1 in 4500
2
Q
Example of genital abnormalities
- 2 newborns - baby A and B
- Both genitically male
- doctors advise parents and perform surgery => female
- Baby A : happy, twenties (2004); married woman
- Baby B : never happy, years of depression, began testosterone treatment; lives as a man.
- At fault - doctor presuming that … + … provided a solution
A
Example of genital abnormalities
- 2 newborns - baby A and B
- Both genitically male
- doctors advise parents and perform surgery => female
- Baby A : happy, twenties (2004); married woman
- Baby B : never happy, years of depression, began testosterone treatment; lives as a man.
- At fault - doctor presuming that surgery + hormones provided a solution
3
Q
What makes a boy/girl involves 3 main events:
- Sex determination, during …
- Differentiation of …, week …
- Differentiation of … and … genital organs, after week …
A
- Sex determination, during fertilization
- Differentiation of gonads, week 5
- Differentiation of internal and external genital organs, after week 5
4
Q
Sex Determination
- Sex is determined at …
- Inheritance of X/Y from …
A
- Sex is determined at fertilization
- Inheritance of X/Y from father
5
Q
Gonad Origin and Diff
- At week … primordial germ cells (PGCs) arise from the …
- PGCs are …potent
- PGC’ migrate to … … stalk to avoid becoming imprinted
- Later return, travelling to the genital … (next to kidney) and become the … gonad
A
- At week 2 primordial germ cells (PGCs) arise from the epiblast
- PGCs are pluripotent
- PGC’ migrate to yolk sac stalk to avoid becoming imprinted
- Later return, travelling to the genital ridge (next to kidney) and become the indifferent gonad
6
Q
Gonad Origin and Diff (2)
- At genital …: XX PGCs replicate at …; XY PGCs replicate at the …
A
At genital ridge: XX PGCs replicate at cortex; XY PGCs replicate at the medulla
7
Q
Gonad gender decision relies on:
- Genetic …
- H…
Genetic …:
- general … factors,
e. g. Wt1, Sf1 - specific promoters of … development
e. g. Sry, Sox9 - specific promoters of … development
e. g. Wnt-4, FoxL2
A
- Genetic switches
- Hormones
Genetic switches:
- general transcription factors,
e. g. Wt1, Sf1 - specific promoters of testis development
e. g. Sry, Sox9 - specific promoters of ovarian development
e. g. Wnt-4, FoxL2
8
Q
Genetic switches:
- general transcription factors,
- e.g. W.., S..
- specific promoters of testis development
- e.g. S…, S…
- specific promoters of ovarian development
- e.g. …-4, …L2
A
- general transcription factors,
- e.g. Wt1, Sf1
- specific promoters of testis development
- e.g. Sry, Sox9
- specific promoters of ovarian development
- e.g. Wnt-4, FoxL2
9
Q
Fate of Gonad Cell lines
- Fill in blanks where arrows are (what gender, what each makes)
A
- Left (Female) - follicular cells, oocytes, internal theca cells - future ovary
- Right (male)- ley dig cells, Pre-spematognia, sertoli cells - future testis
10
Q
Fate of Gonad Cell Lines
- Female PGCs => … (primary oocytes)
- Sex cord cells => … (support and nutrifying the …)
- Cortex => layer of … cells => secrete … before those generated by the follicles
A
- Female PGCs => oogonia (primary oocytes)
- Sex cord cells => granulosa (support and nutrifying the ovum)
- Cortex => layer of thecal cells => secrete androgens before those generated by the follicles
11
Q
Fate of Gonad Cell Lines
- Male PGCs => …
- … influences definition + identity of … cells => secretion of AMH (Anti-Müllerian Hormone)
- AMH supresses … development pathway
- AMH induce cells in intermediate mesoderm to become … => secrete …
A
- Male PGCs => spermatogonia
- Sry influences definition + identity of Sertoli cells => secretion of AMH (Anti-Müllerian Hormone)
- AMH supresses female development pathway
- AMH induce cells in intermediate mesoderm to become leydig => secrete testosterone
12
Q
Kidney Development
- Origin: intermediate … (as the reproductive organs)
- Where: between the … and … plate (each side of the aorta)
- 3 Stages:
- … - disappears soon after
- … - leaves remnants
- … - becomes kidney
A
- Origin: intermediate mesoderm (as the reproductive organs)
- Where: between the somites and lateral plate (each side of the aorta)
- 3 Stages:
- Pronephros - disappears soon after
- Mesonephros - leaves remnants
- Metanephros - becomes kidney
13
Q
Pronephros stage of kidney development - what is it?
A
kidney develops and degenerates straight after (the pronephros is a rudimentary, nonfunctional kidney that appears during the third week of development (eight- to nine-somite stage) and regresses by the fifth week.)
14
Q
- Gonads are … at start
- They are linked to … development
- The middle stage of … development (…) leaves behind ducts that become integral part of the reproductive system
A
- Gonads are indiferent at start
- They are linked to kidney development
- The middle stage of kidney development (mesonephros) leaves behind ducts that become integral part of the reproductive system
15
Q
Internal Genital Organs
- Begin differentiation at about week …, formed from a priori identical primordium structures, i.e
- embryos of … … possess two sets of paired ducts at the start:
- … a.k.a. Müllerian
- … a.k.a. Wolffian
- embryos of … … possess two sets of paired ducts at the start:
A
- Begin differentiation at about week 8, formed from a priori identical primordium structures, i.e
- embryos of both sexes possess two sets of paired ducts at the start:
- paramesonephric a.k.a. Müllerian
- mesonephric a.k.a. Wolffian
- embryos of both sexes possess two sets of paired ducts at the start:
16
Q
Internal Genital Organs - in female embryo
- In female embryo: … duct is kept due to the absence of …
- … duct => becomes … (4)
- …
- …
- …
- upper part of the …
A
- In female embryo: Müllerian duct is kept due to the absence of AMH
-
Müllerian duct =>
- oviduct
- uterus
- cervix
- upper part of the vagina
17
Q
Internal Genital Organs - in male embryo
- In male embryo:
- … causes Müllerian duct regression
- testosterone promotes … duct differentiation
- … duct => becomes (3)
- …
- vas …
- … vesicle
A
- In male embryo:
- AMH causes Müllerian duct regression
- testosterone promotes Wolffian duct differentiation
-
Wolffian duct =>
- epididymis
- vas deferens
- seminal vesicle
18
Q
External Genital Organs
- At first embryos of both sexes show an elevated midline swelling – genital …
- This consists of:
- … groove (opening into the urogenital sinus)
- paired urethral …
- paired … swellings
A
- At first embryos of both sexes show an elevated midline swelling – genital tubercle
- Tubercle consists of :
- urethral groove (opening into the urogenital sinus)
- paired urethral folds
- paired labioscrotal swellings
19
Q
External Genital Organs - Male
- Some testosterone is converted into … (…)
- This stimulates development of the …, … and external genitals (… and …)
- Genital tubercle => …
- Fusion of the urethral folds => spongy …
- Labioscrotal swellings => …
A
- Some testosterone is converted into dihydrotestosterone (DHT)
- This stimulates development of the urethra, prostate and external genitals (scrotum and penis)
- Genital tubercle => penis
- Fusion of the urethral folds => spongy urethra
- Labioscrotal swellings => scrotum
20
Q
External Genital Organs - Female
- Absence of …
- Genital tubercle => …
- Urethral folds remain open => labia …
- Labioscrotal swellings => labia …
- Urethral groove => …
A
- Absence of DHT
- Genital tubercle => clitoris
- Urethral folds remain open => labia minora
- Labioscrotal swellings => labia majora
- Urethral groove => vestibule
23
Q
Turner’s Syndrome:
- Monosomy, …
- Affects how many people?
- What gender?
- …% non-viable embryos
- Survivors fail to sexually mature at …
- Exhibit several … abnormalities (next slide)
- Diagnosis confirmed through …
A
- Monosomy, XO
- 1:2500 females (does not affect males)
- 99% non-viable embryos
- Survivors fail to sexually mature at puberty
- Exhibit several physical abnormalities (next slide)
- Diagnosis confirmed through amniocentesis
24
Q
3 common sign of Turner’s syndrome are:
A
- rudimentary gonads
- lack of menstruation
- lack of breast development
25
Q
Klinefelter’s Syndrome:
- Karyotype is …, Sex genes are …
- How many people?
- What gender?
- Birth appear …
- Become …
- Exhibit some features associated with … development (e.g. …)
- Diagnosis confirmed through …
A
- 47, XXY
- 1:600-1000 male births (does not affect females)
- Birth appear normal (undetected)
- Become infertile
- Exhibit some features associated with female development (e.g. gynecomastia)
- Diagnosis confirmed through amniocentesis
26
Q
Klinefelter’s Syndrome - common signs include:
A
- presence of breasts
- shrunken testes
- deposition of fat (hips etc)
33
Q
Gonadal dysfunction
- e.g. XY gonadal dysgenesis, a.k.a. … Syndrome
- Associated with … karyotype
- Cause: alteration to … gene
- External appearance: … (no …)
- No functional gonads (no … differentiation)
- Gonad may develop into …
A
- e.g. XY gonadal dysgenesis, a.k.a. Swyer’s Syndrome
- Associated with XY karyotype
- Cause: alteration to Sry gene
- External appearance: female (no menstruation)
- No functional gonads (no testicular differentiation)
- Gonad may develop into malignancy
34
Q
Tract Abnormalities
- Some examples:
- Uterine: e.g. … uterus
- Vagina: e.g. …
- Ductus Deferens: … or … absence, failure of … duct to differentiate
A
- Some examples:
- Uterine: e.g. unicornuate uterus
- Vagina: e.g. agenesis
- Ductus Deferens: unilateral or bilateral absence, failure of mesonephric duct to differentiate
39
Q
The Brain and Behaviour: Sexual Differentiation - Example
- In mouse embryos, … genes are expressed differently between male and female brain prior to advent of sex hormones (RT-PCR)
- These genes are active before … even develop, let along …, about week … of development
A
- In mouse embryos, 51 genes are expressed differently between male and female brain prior to advent of sex hormones (RT-PCR)
- These genes are active before gonads even develop, let along differentiate, about week 2 of development
