Sexual differentiation Flashcards
D: Sex
the process by which a genetically novel individual is formed as the result of mixing of genes from two or more individuals
is the female homogatetic?
yes in humans.
not always teh case for other organsisms
how did the y chromosome evolve?
male sx determining gene on the proto Y chromosome
male advantageous genes accumulate
inversions prevent recombination. - evolve separately
non coding repetitive sequences deleted.
what is your gonadal sex?
determine by the genetic sex
whether you have a testis or an aovary
what is your somatic sex?
whether you have a penis scrotum & prosatate
vs clit vagina uterus and oviduct
what is your neuroendocrine sex?
HPG axis
whether its constant (male) or cyclical (female)
describe turnedrs syndrome
where you only ahve a single X chromosome
(depends if it comes from the mother or father)
what is kleinfelters syndrome?
XXY
bascially a male
small poorly functioning testicles.
how can you have an XX male?
when part of the sex determining region of the Y is translocated onto the X chromosome
can you have an XY female?
yes - sex determining part fo the Y is deleted
what is SRY
encodes DNA/RNA binding protein 200 AA long
has the HMG box - which binds DNA
its a transcription factor
Binds to other genes eg SOX9 – initiates cascades of gene expression.
Genital ridges form during _th and _th weeks on medial side of the mesonephric ridges
Genital ridges form during 5th and 6th weeks on medial side of the mesonephric ridges
what colonises the genital ridges?
Colonised by primordial germ cells migrating from the extraembryonic mesoderm close to the yolk sac.
wehat happens to the genital redges in males?
they form the sex cords - becoming the spermatogenic tubules
what happens to the sex cords in females?
sex cords break down – form clusters of cells aroud each PGC – become follicles
describe how the testis forms in males
- SRY switched on in cells of the sex cords (sertoli cells)
- sertoi cells proliferate to form seminiferous tubules
- SRY also switched on in stromal cells (Leydig cells)
- Seminiferous tubules connect with degenerating mesonephric tubules of the rete testis.
- Androgens from Leydig cells maintain the mesonephric duct, and MIS from Sertoli cells stimulates degeneration of the paramesonephric duct.
Androgens from Leydig cells maintain the ______ ____, and MIS from Sertoli cells stimulates degeneration of the _______ _____
Androgens from Leydig cells maintain the mesonephric duct, and MIS from Sertoli cells stimulates degeneration of the paramesonephric duct.
leydig cells secrete?
androgens
sertoli cells secrete?
MIS
describe how the ovaries are formed in females:
- no SRY
- Sex cords degenerate
- Coelomic epithelium proliferates to form cortical cords.
- Cells from cortical cords surround oogonia to form primordial follicles.
- Absence of androgens causes mesonephric duct to degenerate.
- Absence of MIS permits maintenance of the paramesonephric duct.
what does insulin like hormone 3 do?
stimulates the gubernaculuym to contract
= testis decent
androgen cause the developemetn of what in males?
penis, scrotum
vasa,
accessort sex glands
Differentiation of the external genitalia is driven primarily by…
Differentiation of the external genitalia is driven primarily by dihydrotestosterone (DHT)
describe how DHTis produced
DHT is produced from testosterone by the activity of the enzyme 5 alpha reductase that is present in the local tissues
Absence of this enzyme (% alpha Reductase) leads to…..
Absence of this enzyme leads to female genitalia (Guevodoces)
describe Güevedoce
Güevedoces (roughly translated as “penis at twelve”) is a term used in the Dominican Republic for children with a specific type of intersexuality.
Güevedoces are classified as girls when they are born but, around the age of 12, they start developing male genitalia. T
his is due to a deficiency in the production of 5α-reductase, an enzyme involved in the metabolism of testosterone to dihydrotestosterone.
puberty = lots of testosterone = male charactertisics develope
wat drives external gential developement
5 alpha reductase – testosterone –> DHT – drives external genetalia development
in what ways may the bain be masculinised?
Structural – e.g. size of certain areas
Chemical – e.g. level of transmitters
Physiological – e.g. metabolism, cyclicity
Psychological – e.g. gender, aggression
Cognitive – e.g. verbal fluency, spatial ability
Primary hermaphroditism
describe1
- Anomalies of gonad
- Ovary one side, testis on other
- 2 gonads – mix of gonadal tissue – non functional
- Mutational event during gestation – early – don’t cross midline = truw hermaphrodite
- Later in developemtn – moscaisism = mix
- Mutational event during gestation – early – don’t cross midline = truw hermaphrodite
describe secondary hermaphrodiatism
anomalies of the soma
Testicular feminisation (androgen insensitivity syndrome)
Congential adrenohyperplasia
Micropenis
Hypospadias
describe
Androgen insensitivity syndrome
(testicular feminisation)
XY male
normal sexual appearance
normal internal testis and androgen production
MIS production = no paramesonephric duct
external genitalia = female
no uterus, fallopian tube or upper vagina
- 400 mutations known in androgen receptor – altering its function in many parts of life cycle.
- Leads to spectrum – depending how function AR is
describe congenital adrenal hyperplasia
- 21 hyroxylase dysfunction - an enzyme used to produce cortisol. leads to precursor build up = more testosterone.
- XX people can end up with lots of testosterone
- = masulinisaed external genitalia
describe 5-alpha-reductase deficiency
Guevedoces
XY people. lacking potent DHT
lack of external male appearance at birth
puberty = lots of testosterone - start developing of external genitalia (albeit small)
Psychosexual development: what do these terms mean
Gender identity –
Gender role –
Sexual orientation –
Psychosexual development:
Gender identity – self representation
Gender role – toy preferences, physical aggression – society dependant
Sexual orientation – erotic interes
is gencer learned?
- Evidence for yes – depending on how you trewaat your babies
- Babies repsonses – toys and clothes, environment
- 2-4 years – learn gender role
- Learn how to play the gender role
- By 5 – fixed about gender – male or female – leads to gender policing of each other.
- If boy behaves like a girl – children police this
what is sexuality?
Classed by object of erotic attraction
Sexual sterotypes; behaviours
is sexuality fixed?
no
Man ____ likely to identify as gay rather than bisexual
Man more likely to identify as gay rather than bisexual
fat
mamba
