SEX Differentiation by.R.Bundak

7/25/2019 SEX Differentiation by.R.Bundak

1/33

Sexual Differentiation

Sexual Differentiation

Prof.Dr. Rveyde BUNDAK

Prof.Dr. Rveyde BUNDAK


2/33

Sex determination and

differentiation

Sex determination and

differentiation

is a sequential process tat

involves at least fourcaracteristics tat aredelineated in various sta!es

is a sequential process tat

involves at least fourcaracteristics tat aredelineated in various sta!es


3/33

Fertilisation Genetic sex

Genetic sex Gonadal sex

Gonadal sex Phenotypic sex

Hormones + Social environment Psychologic sex

Gender identitiy


4/33

"enetic sexis determined atfertili#ation

"onadal sexis determined $y !eneticsex

Sexual differentiation of te !onadsleads to te development of internal!enital tracts and te external

!enitalia and ence te %Penotypicsex&

"enetic sexis determined atfertili#ation

"onadal sexis determined $y !eneticsex

Sexual differentiation of te !onadsleads to te development of internal!enital tracts and te external

!enitalia and ence te %Penotypicsex&


5/33

'e development of seconder sexcaracteristics provides additional

visi$le penotypic manifestations atpu$erty.

Psycolo!ical sexual identity is

acquired postnatally $y sociolo!icalimprintin! on te developin!personality.

'is postnatal process(to!eter )itprenatal ormonal influences(dedected te !ender identity or

psycolo!ical sex.

'e development of seconder sexcaracteristics provides additional

visi$le penotypic manifestations atpu$erty.

Psycolo!ical sexual identity is

acquired postnatally $y sociolo!icalimprintin! on te developin!personality.

'is postnatal process(to!eter )itprenatal ormonal influences(dedected te !ender identity or

psycolo!ical sex.


6/33

"enetic sex

"enetic sex


7/33

The human genomeconsists of two copies

of each of 23 chromosomes (a total of 46).One set of 23 comes from the mother andone set comes from the father. Of these23 pairs of chromosomes, 22 areautosomes, and one is a sex chromosome.There are two inds of sexchromosomes!"#" and "$". %n humans and in

almost all other mammals, females carr&two # chromosomes, designated ##, andmales carr& one # and one $, designated

#$.
http://en.wikipedia.org/wiki/Human_genomehttp://en.wikipedia.org/wiki/Human_genome


8/33

' human egg contains onl& one set ofchromosomes (23) and is said to e haploid.perm also ha*e onl& one set of 23

chromosomes and are therefore haploid.+hen an egg and sperm fuse at fertiliation,the two sets of chromosomes come together

to form a uni-ue "diploid" indi*idual with 46chromosomes.


9/33

Human Karyotype


10/33

The sex chromosome in a human egg isalwa&s an # chromosome, since a female

onl& has # sex chromosomes. %n sperm,aout half the sperm ha*e an # chromosomeand half ha*e a $ chromosome. %f an egg

fuses with a sperm with a $ chromosome,the resulting indi*idual is usuall& male. %f anegg fuses with a sperm with an #chromosome, the resulting indi*idual isusuall& female. 'n eggs sex chromosome isalwa&s an #, so it is the sperms sexchromosome that determines an indi*iduals

sex


11/33


12/33


13/33

"onadal sex

and

Penotypic sex

"onadal sex

and

Penotypic sex


14/33

Sex is not really determined bychromosomes

Genes are the underlying basis for sex

determination

Some on sex chromosomes, others onautosomes


15/33


16/33

Intrauterine sexual differentiation

Differentiation of gonads,

Differentiation of internal genital ducts,Differentiation of external genitalia

I. Differentiation of gonads:-Until approximately ! days of gestation

embryonic gonads of males and females are

indistinguishable, there is a primiti"e gonadal structure

-Subse#uent differentiation of gonads into testes oro"ary depends on the presence of testes determining

gene or Sex determining Region of Y on

$ chromosome


17/33


18/33

%Dr& 'eter Koopman (asable to pro"e that the S)$

gene is the *D+ from

studies on male

%S)$ is $ specific, andthere is no analogue on the

chromosome


19/33


Genes important for gonadal diff.

SRY gene:-n short arm of $ chromosome, in close proximity (ith

pseudoautosomal region&-S)$ codes for a D./ binding protein and facilitates transcription

of do(nstream genes&-Deletion of S)$ in a 0 $ person results in female de"elopment

(ith dysgenetic gonads

-*ransfection of S)$ into 0 mice embryo

results in male de"elopment (ith testes 1but sterile2-During meiosis in male , pseuodoautosomal regions of the and $chromosomes are exchanged&

-During this exchange, S)$ can be transferred to the chromosome

1 males2


20/33

/enital ridge+T0

10 im0

mx2 1gf

5ipotential gonad

'#0 SR*

+nt4 O#

78T2

'T8#

O*ar& Testes

Somatic cells "erm cells

+ullerian ducts ,-/olffian ducts ,0

1xternal !enitalia


21/33

Testes

Sertoli cells Leydig cells

AM LR AMR StAR

!"SD#

$Y%&'(%)R

SD&'"!

*aR

*estosterone DH*

AR AR

34llerian ducts 1-2 5olffian ducts 162

7nternal Genitalia 8xternal Genitalia


22/33


23/33

-9y ! days of gestation germ cells appear-7f SRYis present, :-;< days ---= differentiation

into T+ST+S

>eydig cells ? 0< days3ale external genitalia ? 0;-@@ days

-7f SRYis not present, (ithin @@-A days

primiti"e gonad differentiates into-------= ),ARY


24/33

ther genes important for gonadal diff&

DSS gene:is on short arm of Bhromosome

-Dosage sensiti"e sex re"ersal gene

-Dublication of DSS gene in a 0 $ embryo results

in 0 $ females

5*-C gene1Denny-Drash , 5/G) syndrome2

S- gene1Bamptomelic d(arfism2


25/33

Intrauterine sexual differentiationII. Differentiation of internal genital ducts

-Up to @ (eeEs? no internal duct differentiation

primordial structure contains both3ullerian and 5olfian ducts

-/fter @ (eeEs? de"elopment of internal genital ducts depends on

the presence or absence of a functional fetal testes and completed

by C! (eeEs& -+etal testes secrete t(o different substances?

1. Mullerian inhibiting factor (MIF, AMH) -by Sertoli cells?

causes regression of 3ullerian ducts1ipsilaterally2

!. "estosterone-by >eydig cels?

a2 causes further de"elopment of 5olfian ducts

b2by being con"erted to dih#drotestosteron(DHT2

promotes masculiniFation of external genitalia


26/33

-7n the female fetus,there is no testes --= no 37+--= 3ullerian duct de"elops further

--= no testosteron---= regression of 5olfian ducts

Mullerian ducts: Uterus, +allopian tubes, cer"ix C: upper part of the "agina

-olfian ducts? as deference, epididymis, seminal

"esicles, eIaculatory duct


27/33


28/33


29/33

Gonadal differentiation

Intra terine se al differentiation


30/33


II. Differentiation of external genitalia:

-Britical period 1A-C! (eeEs2

-Up to A (eeEs, no external genital differentiation is present-*here is a primiti"e external genital structure (hich

contains?

Male Female

Genital tu/ercle? Glans penis Blitoris%0ret1ral folds: Shaft of the penis >& minora

%0ret1ral groo2e: 'enile uretra >o(er !: "agina&

%La/ioscrotal s3elling Scrotum >& maIora

-7f testes, DH*, and androgen receptor present? differentiation into

male external genitalia completed by C0 (eeEs&


31/33

DT:binds to androgen receptor on genital structuresand causes?

-fallic enlargement -Fipping-up genital groo"e into penile urethra

-Fipping-up labioscrotal s(elling into scrotum

-prostate gro(th


32/33

S12 D3441R1N'3A'35NBipotential "onad

6 )ee7,/

Di8i y9nnde

22

"enes S52: S52;

'estes,


33/33

Documents

SEX Differentiation by.R.Bundak