Sex determination and differentiation Flashcards
Studies of structural aberrations of the human Y chromosome reveal that maleness is determined by a _____ located on the ____ of the Y chromosome.
testis – determining factor (TDF); short arm
If the the TDF region is absent, the undifferentiated gonad becomes an ____ and sex differentiation occurs along ____ lines.
ovary; female
In the presence of the TDF, a testis forms. The _____ of the seminiferous tubules secrete a Mullerian duct inhibitor, and anti – Mullerian hormone (AMH), w/c causes regression of the primitive uterus.
sertoli cells
In the presence of the TDF, a testis forms. The Sertoli cells of the seminiferous tubules secrete a ____, and ____, w/c causes regression of the primitive uterus.
Mullerian duct inhibitor; anti – Mullerian hormone (AMH)
In the presence of the TDF, a testis forms. The ____ of the testis secrete testosterone, which both stimulates the Wolffian ducts to differentiate into the epididymis, vas deferens and seminal vesicles, & also masculinizes the external genitalia.
interstitial cells
In the presence of the TDF, a testis forms. The interstitial cells of the testis secrete testosterone, which both stimulates the ____ to differentiate into the _____, ____ and _____, & also masculinizes the external genitalia.
Wolffian ducts; epidedymis, vas deferens; seminal vesicle
The gene ____ has been confirmed as the master - switch TDF in humans and mice by mutation analysis in cases of sex reversal.
SRY (sex - determining region of the Y)
T/F. The gene maps within the sex - determining region, is expressed in the undifferentiated gonad at an appropriate time in development and, in the mouse, causes sex reversal when introduced into male pre - embryos .
False. Causes sex reversal only in female embryos.
How does SRY act as a transcription factor?
SRY protein binds to DNA at a specific 6 - nucleotide target sequence and is believed to act as a transcription factor by causing the DNA to bend through a specific angle
An important downstream effector of SRY is thought to be the ____ gene on human chromosome ____. In turn, the SOX9 protein appears to regulate the expression of ____.
SOX9; 17; Anti-Mullerian Hormone
T/F. The location of SRY inside the pairing segment on the short arm of the Y normally ensures that recombination does not transfer the TDF to the X chromosome.
False. SRY is located outside XY pairing region
T/F. SOX9 gene is highly dosage - sensitive.
True. As duplication of the gene has been reported to induce male development in the absence of SRY (i.e. causing XX sex reversal), while SOX9 haploinsufficiency can prevent male development in the presence of SRY (i.e. causing XY sex reversal).
In XY females is due to?
deletions or mutations affecting SRY
XX males is due to?
transfer of SRY to the X chromosome due to accidental recombination
