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Sexual Differentiation
Sexual Differentiation
Prof.Dr. Rveyde BUNDAK
Prof.Dr. Rveyde BUNDAK
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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
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Fertilisation Genetic sex
Genetic sex Gonadal sex
Gonadal sex Phenotypic sex
Hormones + Social environment Psychologic sex
Gender identitiy
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"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 $y !eneticsex
Sexual differentiation of te !onadsleads to te development of internal!enital tracts and te external
!enitalia and ence te %Penotypicsex&
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'e development of seconder sexcaracteristics provides additional
visi$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 $y sociolo!icalimprintin! on te developin!personality.
'is postnatal process(to!eter )itprenatal ormonal influences(dedected te !ender identity or
psycolo!ical sex.
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"enetic sex
"enetic sex
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The human genomeconsists of two copies
of each of 23 chromosomes (a total of 46).One set of 23 comes from the mother andone set comes from the father. Of these23 pairs of chromosomes, 22 areautosomes, and one is a sex chromosome.There are two inds of sexchromosomes!"#" and "$". %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_genome7/25/2019 SEX Differentiation by.R.Bundak
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' 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.
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Human Karyotype
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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
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"onadal sex
and
Penotypic sex
"onadal sex
and
Penotypic sex
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Sex is not really determined bychromosomes
Genes are the underlying basis for sex
determination
Some on sex chromosomes, others onautosomes
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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
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%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
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Intrauterine sexual differentiation
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
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/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
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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
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-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
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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
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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
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-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
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Gonadal differentiation
Intra terine se al differentiation
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Intrauterine sexual differentiation
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&
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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
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S12 D3441R1N'3A'35NBipotential "onad
6 )ee7,/
Di8i y9nnde
22
"enes S52: S52;
'estes,
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