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Questions and Answers
Which duct system is associated with the development of testes?
Which duct system is associated with the development of testes?
- Müllerian duct
- Wolffian duct (correct)
- Oviduct
- Cloacal duct
What role do Lhx9 and Gata4 play in gonadal sex determination?
What role do Lhx9 and Gata4 play in gonadal sex determination?
- They function solely in the development of Wolffian ducts
- They promote only ovary formation
- They inhibit the SRY gene
- They activate Wnt and Rspo1 (correct)
What does the SRY gene influence in male sex determination?
What does the SRY gene influence in male sex determination?
- Initiates gonadal sex differentiation (correct)
- Promotes Wolffian duct formation
- Inhibits Müllerian duct development
- Regulates hormone levels only
What is the primary role of the Y chromosome in male sex determination?
What is the primary role of the Y chromosome in male sex determination?
Which of the following best defines primary sex determination?
Which of the following best defines primary sex determination?
What outcome is associated with XX humans who have RSPO1 mutations?
What outcome is associated with XX humans who have RSPO1 mutations?
What happens in XY individuals with a duplication of the region containing WNT4 and RSPO1?
What happens in XY individuals with a duplication of the region containing WNT4 and RSPO1?
What is true about individuals with XY chromosomes?
What is true about individuals with XY chromosomes?
What does the term 'bipotential' refer to in early embryonic gonads?
What does the term 'bipotential' refer to in early embryonic gonads?
What is secondary sex determination primarily influenced by?
What is secondary sex determination primarily influenced by?
What is the primary role of estrogens in females during secondary sex determination?
What is the primary role of estrogens in females during secondary sex determination?
Which phenotype is associated with individuals who are XXY?
Which phenotype is associated with individuals who are XXY?
What effect does testosterone have on the development of male genitalia?
What effect does testosterone have on the development of male genitalia?
Why is the second X chromosome critical in the context of sex determination?
Why is the second X chromosome critical in the context of sex determination?
Which of the following is a potential application of stem cells?
Which of the following is a potential application of stem cells?
What is the result of the secretion of Müllerian-inhibiting substance by Sertoli cells in males?
What is the result of the secretion of Müllerian-inhibiting substance by Sertoli cells in males?
What distinguishes primary sex determination from secondary sex determination?
What distinguishes primary sex determination from secondary sex determination?
How do females compensate for having two X chromosomes compared to males in terms of gene transcription?
How do females compensate for having two X chromosomes compared to males in terms of gene transcription?
What primary sex characteristic is typically present in individuals with androgen insensitivity syndrome?
What primary sex characteristic is typically present in individuals with androgen insensitivity syndrome?
In which taxonomic group is sex determination primarily influenced by temperature during embryonic development?
In which taxonomic group is sex determination primarily influenced by temperature during embryonic development?
What process is primarily responsible for gonadal differentiation into either testes or ovaries?
What process is primarily responsible for gonadal differentiation into either testes or ovaries?
What is primarily affected in individuals with Androgen Insensitivity Syndrome (AIS)?
What is primarily affected in individuals with Androgen Insensitivity Syndrome (AIS)?
What key function does dihydrotestosterone (DHT) serve in male development?
What key function does dihydrotestosterone (DHT) serve in male development?
Which of the following statements about secondary sex determination is accurate?
Which of the following statements about secondary sex determination is accurate?
What is the difference between primary and secondary sex determination?
What is the difference between primary and secondary sex determination?
In terms of sex determination systems, which of these is not typically characterized as an example of environmental sex determination?
In terms of sex determination systems, which of these is not typically characterized as an example of environmental sex determination?
What is the role of the Sry gene on the Y chromosome?
What is the role of the Sry gene on the Y chromosome?
What result occurs when the Sry gene is translocated to the X chromosome in an XX individual?
What result occurs when the Sry gene is translocated to the X chromosome in an XX individual?
What primary sexual characteristic is expected in an XX/Sry mouse?
What primary sexual characteristic is expected in an XX/Sry mouse?
Which of the following statements about men with ovotestes is true?
Which of the following statements about men with ovotestes is true?
What does secondary sex determination involve?
What does secondary sex determination involve?
What is a characteristic of the external genitalia in an XX/Sry mouse compared to an XY mouse?
What is a characteristic of the external genitalia in an XX/Sry mouse compared to an XY mouse?
What effect does the presence of two X chromosomes have on the seminiferous tubules in an XX mouse with Sox9 transgene?
What effect does the presence of two X chromosomes have on the seminiferous tubules in an XX mouse with Sox9 transgene?
What happens in mammals when Sry is activated late during development?
What happens in mammals when Sry is activated late during development?
Study Notes
Sex Determination in Mammals
- The presence of a Y chromosome initiates the development of testes.
- The gonads in early embryonic mammals are bipotential meaning they can develop into either testes or ovaries.
- The Y chromosome contains the SRY gene, which is a transcription factor that activates the Sox9 gene.
- Sox9 is a key gene for testis formation.
- In the absence of a Y chromosome, the gonads develop into ovaries. During this process, a transcription factor called Wnt4 is activated, which inhibits Sox9 expression.
- The presence of WNT4 and RSPO1 genes on chromosome 1 can cause a male-to-female sex reversal.
Secondary Sex Determination in Mammals
- Secondary sex determination in mammals is regulated by hormones secreted by the testes and ovaries.
- These hormones influence the development of male or female phenotypes, including the internal reproductive organs, external genitalia, and other secondary sexual characteristics.
- Testosterone determines male secondary sex determination, and estrogens determine female secondary sex determination.
Environmental Sex Determination
- Some animals, like reptiles, use temperature cues to determine sex.
- This mechanism is known as temperature-dependent sex determination (TSD).
- The sex of the offspring is determined by the temperature at which the embryos are incubated during a specific period of development.
- Some reptile species, like turtles and crocodilians, have a specific temperature range for male development and another range for female development.
- Different species have different temperature thresholds for sex determination.
Key Takeaways
- Sex determination in mammals is a complex process involving genetic and hormonal cues.
- Primary sex determination depends on the presence or absence of the Y chromosome.
- Secondary sex determination is regulated by specific hormones, resulting in male or female phenotypes.
- Environmental sex determination, seen in reptiles and some other species, uses temperature as a cue for determining sex.
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Description
Explore the mechanisms of sex determination in mammals, focusing on the role of the Y chromosome and key genes such as SRY and Sox9. Understand how hormones influence secondary sex characteristics and the implications of gene interactions in sex reversal. Ideal for biology students studying mammalian development.
