Question
Trace the sequence of events turning default female sex of the fetus into male :
(a) SRY gene produces Sry protein
(b) Presence of Y chromosome
(c) Testosterone masculanize Wolffian duct into seminal vesicles
(d) Primitive gonad develop into testes
(e) Mullerian inhibiting hormone defeminizes the fetus
The correct answer is
(b), (a), (d), (e), (c)
Male Fetal Sex Determination: Sequence of Events
Understanding the sequence that directs fetal development towards the male phenotype is crucial. The default pathway leads to female characteristics; thus, specific genetic and hormonal signals initiate male differentiation.
Key Stages in Male Development
- Y Chromosome Presence (b): The genetic blueprint begins with the presence of the Y chromosome.
- SRY Gene Activation (a): The SRY gene, located on the Y chromosome, is activated and produces the critical Sry protein.
- Testes Differentiation (d): The Sry protein directs the primitive gonads to develop into testes.
- Defeminization (e): The developing testes secrete Mullerian inhibiting hormone (MIH), causing the Mullerian ducts to regress, preventing female internal structure formation.
- Masculinization (c): The testes also produce testosterone, which acts on the Wolffian ducts, promoting their development into male reproductive organs like seminal vesicles.
This precise order of events is essential for successful male sexual differentiation.
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Important Questions from System Physiology Animal
- Read each of the following two statements - Assertion (A) and Reason (R) and indicate your answer using the codes given below :
Assertion (A) : Castration does not eliminate sexual behaviour completely in mammals, including humans, of both sexes.
Reason (R) : Hormones do not play role in the regulation of sexual behaviour. - When is aspiration a method of choice to make a lesion ?
- Autonomic Nervous System is concerned with the regulation of _______ .
I. Smooth muscles
II. Skeletal muscles
III. Cardiac muscles
IV. Glands
Codes : - Given below are two statements, one labelled as Assertion (A) and the other labelled as Reason (R) :
Assertion (A) : A positive charge applied to the inside of the membrane of the neuron produced depolarization.
Reason (R) : Inside of the membrane was positively charged.
In the context of the above two statements, which one of the following is correct ?
Codes : - Which one of the following events is critical for the development of internal sex organs in males during 3rd month of gestation ?
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