Chapter 6: Sexual Development Flashcards
Genetic Sex?
- set at fertilization
Jost’s study with rabbits revealed what about genetic sex?
- female development is the default pathway
- removal of the ovaries = no change in development
- removal of testicles = development into females
Sex is usually determined by the presence of what gene located on the Y chromosome?
- SRY gene
SRY Gene:
- Any embryo that possesses at least one _ chromosome will develop into a male (with some exceptions)
- Y
Atypical Development: 1. Turner's Syndrome? L> issue with? L> physical appearance ? L> cognitive deficits? L> first indicator? L> treatment?
- single x chromosome or a truncated portion of an c chromosome
L> physically— shrunken ovaries, no gland or hormones, short stature, some other etc …
L> cogntiive deficits: visuospatial difficulties, memory and attention probs
L> webbed neck = first indicator
L> treatment= GH, androgens and estrogen
Atypical Development: 2. Klinefelter's Syndrome - location of issue? - physical symptoms? L> when do they become full blown? - endocrinological flaws?
- single Y chromosome, multi x…ex XXY
- gynecomastia (enlargement of breast tissue in males)
- feminine body contours, sparse facial hair and body hair
- full syndrome at puberty
- low testosterone levels
- sperm count is too low for normal fertility
- no sex drive
The SYR gene and others direct the development of the ___.
gonads
SYR gene and others directing gonads:
1. Sexual differentiation in both/one sex involves both ___ and ___.
- both
- gene activation and suppression
SYR gene and others directing gonads:
2. At five weeks post-conception, male embryos begin to what?
- express the SRY gene
SYR gene and others directing gonads:
3. Explain the product of the SYR gene
- transcription factor that turns on other genes such as SOX9 which directs and maintains testicular development
SYR gene and others directing gonads:
4. FOXL2???
- located on the X chromosome , it suppresses SOX9 and the development of testicles
The male and female reproductive tracts develop from similar or different precursors?
- different
The male reproductive tract develops from ___;whereas, the female reproductive tract develops from the ____.
- Wolffian Ducts
- Mullerian
Are both the wolffian and mullerian ducts present in both sexes?
- YES
In males the mullerian duct is suppressed by what?
- anti-Mullerian hormone
Testosterone from the Leydig cells begins being produced at ___ weeks and peaks at - weeks, directing the development of the Wolffian ducts.
- 8 weeks
- 12-16 weeks
Male and female external genitalia develop from the same or different precursors?
- SAME
- homologous - having a common origin / precursors
List which structures of the external genitalia are homologous with each other across sexes.
- scrotum - labia majora
- shaft of penis - labia minora
- glans of penis - glans of clitoris
Do female or male genitalia develop by default?
- female
Does removal of the ovaries change the process of development when it comes to being female?
- no
In male fetuses, testosterone is required/or not required for regular development of the genitalia?
- it is required
- developing genitalia express androgen receptors and 5alpha-reductase ( which converts T to DHT)
Atypical Development:
- Congenital Adrenal Hyperplasia ? (CAH)
- reduced production of?
- excessive growth of ?
- excessive production of?
- What happens to XX individuals?
- Brain Masculinization ?
- treatment?
- reduced production of steroids form the adrenal cortex
- excessive growth of adrenal cortex (compensation mech of body)
- excessive adrogen production
- XX individuals are partially masculinized during fetal and postnatal development (enlarged clitoris, partially fused labia majora)
- brain masculinization:
L> behaviour is more male like in terms of preferences for toys aggressive play etc… higher incidence of sexual attraction to women (37%) - surgical correction
- life long administration of corticosteroids.
When comparing Boys, girls and girls with CAH…how is time divided among boy toys and girl toys?
- boys and CAH girls are fairly close when playing with boy toys.(girls are lower)
- boys and CAH girls are similarly on the low end of playtime with girl toys vs girls.
- Neutral toys they all play about equal
Atypical Development:
2. 5 alpha-reductase deficiency syndrome?
- found in what kind of communities?
- genotype of sex?
L> they develop ovaries or testes?
- they do or do not produce AMH and T
- internal reproductive structures are masculine or feminine ?
- External genitalia develop or do not develop properly?
- typically found in genetically isolated communities
- XY males
- develop testes
- produce AMH(anti-mullerian hormone) and Testosterone
- Internal reproductive structures are masculine
- External genitalia do not develop properly
Atypical Development:
- 5 alpha-reductase deficiency syndrome?
- External Genitalia do not develop properly. Explain (3)
- labia like structures instead of scrotum
- urogenitalia sinus nto which a vaginal pouch and urethra open
- clitoris like penis.
Atypical Development:
- 5 alpha-reductase deficiency syndrome?
- at puberty testosterone not ___ produces typical masculine physical characteristics including the enlargement of the penis.
- not DHT
Atypical Development:
- 5 alpha-reductase deficiency syndrome?
- psychological effects?
- children make an easy transition in some cultures…..with heterosexual orientation (female partners)
Atypical Development:
- 5 alpha-reductase deficiency syndrome?
- in some cultures this is considered what?
- third gender
The dominican republic study, Imperato-McGinley et al. (1974, 1979)
L> explain the study
- subjects?
- syndrome?
- break down of decision at puberty
- what are they called/considered in the DR
- 18 genetic males…XY
- all had 5 alpha reductase deficiency syndrome
-Various responses to changes at puberty
L> one decided he was male but continued to dress as a female
L> one maintained a female gender identity, had a sex change and married a man - 16 readily assumed a male gender identity and gender role
- They are called the Goevedoces of Salinas ….which are considered a third gender.
Atypical Development:
- Androgen Insensitivity Syndrome
- cause?
- ## androgens cannot bind to their receptors or receptor cannot bind to its DNA targets
Atypical Development:
- Androgen Insensitivity Syndrome
- genotype?
- XXY
Atypical Development:
- Androgen Insensitivity Syndrome
- do testes develop? if they do what do they release?
- testes develop and release testosterone and AMH
Atypical Development:
- Androgen Insensitivity Syndrome
- What does AMH cause?
- mullerian ducts to regress
Atypical Development:
- Androgen Insensitivity Syndrome
- does testosterone produced by the testes have an effect?
- no and the Wolffian ducts do not develop
Atypical Development:
- Androgen Insensitivity Syndrome
- external genitalia?
- defaults to female structures
Atypical Development: 3.Androgen Insensitivity Syndrome - does menstruation occur? L> whats the deal with hair? - do breasts develop?If so, why?
- no
- no auxiliary hair or pubic hair.
- yes due to estrogen
Atypical Development:
3.Androgen Insensitivity Syndrome
- will function sexually as a heterosexual female with normal sex drive, frequency of orgasm and intercourse.
Atypical Development:
- Gonadal Intersexuality
- What intersexuality does mean?
- ovarian and testicular tissue (ovotestes) appear in the same person
Atypical Development:
- Gonadal Intersexuality
- in the case of ovarian tissue and testicular tissue which develops normally and which poorly?
- ovarian normally and testicular poorly
Atypical Development:
4. Gonadal Intersexuality
L> appearance of external and internal organs is highly variable or fairly constant across all cases?
- appearance of internal and external organs is highly variable across individuals
Atypical Development:
- Gonadal Intersexuality
- Which structures dominate usually?
- female structures
- most identify as women and look like them (majority actually have XX)
Atypical Development:
- Gonadal Intersexuality
- is it known why testicular tissue develops?
-no
Atypical Development:
4. Gonadal Intersexuality
- some individuals are chromosomal chimeras. What does this mean?
L> how does it occur?
- they possess some cells with XX and some with XY
- two separate conceptuses of differing chromosomal sex fuse early in development…or if two sperm ( one X and one Y) fertilize the ovum.
Sexual Differentiation of the CNS:
- what does it mean to have sexually dimorphic structures?
- phenotypic difference between males and females of the same species.
Sexual Differentiation of the CNS:
- Sexually dimorphic structures
L>in the spinal cord??
- spinal cord …onuf’s nucleus (smaller in females
Sexual Differentiation of the CNS:
- Sexually dimorphic structures
L> In the brain??
- Medial preoptic area of the hypothalamus (MPoA)
L> involved in male typical sexual behaviour… may play a role in the suppression of female typical behaviour
Sexual Differentiation of the CNS:
- Sexually dimorphic structures
L> Within the MPoA the INAH3??
- it is larger in males than females
smaller in homosexual males vs hetero
Sexual dimorphism arises as a consequence of what?
- differing hormonal levels during a sensitive period
Early Hormonal exposure influences what?
- later sexual behaviour
Sexual Differentiation of the CNS:
- Early Hormonal exposure influences later sexual behaviour
L> rodents exp
L> In primates exp
- organizational and activation effects of testosterone ( fig. 617)
- multiple sensitive periods
1. Prenatal testosterone in females:
L> increases play -sex when given in early fetal life
L> increases play-fighting when given later in fetal life
L> increases male typical mounting when these animals reach adulthood when testosterone is administered.
