Sex Determination & DIfferentiation

Question 1

What is the primary difference between sex determination and differentiation?

Answer 1

Sex determination refers to the genetic determination of sex, while differentiation involves the development of physical sex characteristics.

Question 2

What are the different strategies of sex determination used by animal groups?

Answer 2

• Genetic sex determination
• Environmental sex determination
• Social sex determination
• Temperature-dependent sex determination

Question 3

What role does the Y chromosome play in gonadal sex differentiation?

Answer 3

The Y chromosome, through the SRY gene, controls the development of testes, thus determining male gonadal sex.

Question 4

What are the key hormonal products of the gonads that influence secondary sex differentiation?

Answer 4

• Testosterone
• Estrogens
• Anti-Müllerian hormone (AMH)

Question 5

Differentiate between activation and organization effects of hormones.

Answer 5

Activation effects lead to temporary changes in behavior, while organization effects result in permanent changes in the nervous system and behavior.

Question 6

What defines male or female in biological terms?

Answer 6

• Chromosomal sex
• Gonadal sex
• Hormonal sex
• Morphological sex
• Behavioral sex

Question 7

What is the process of sex determination in mammals?

Answer 7

It is determined by the presence or absence of a Y chromosome, leading to the development of male or female phenotypes.

Question 8

How does the ZZ-ZW sex determination system work?

Answer 8

In this system, ZZ represents males and ZW represents females, as seen in birds and some reptiles.

Question 9

What happens in the absence of the SRY gene?

Answer 9

The gonads begin to develop into ovaries instead of testes.

Question 10

What is the role of the SRY gene in sex differentiation?

Answer 10

The SRY gene initiates testes differentiation and inhibits ovarian development.

Question 11

What is the significance of SOX9 in sex differentiation?

Answer 11

SOX9 is turned on by SRY and is crucial for the development of testes and suppression of ovarian development.

Question 12

What are the consequences of the absence of testosterone during development?

Answer 12

The Wolffian ducts degenerate, leading to the development of female internal genitalia.

Question 13

What hormone is responsible for the masculinization of external genitalia?

Answer 13

5α-dihydrotestosterone (DHT)

Question 14

Fill in the blank: The differentiation of the external genitalia is regulated by ______.

Answer 14

androgens

Question 15

What is the default setting for sexual differentiation in the absence of specific hormones?

Answer 15

Female differentiation

Question 16

What is the impact of gonadal hormones during critical periods of development?

Answer 16

They lead to permanent changes in the body, including brain differentiation.

Question 17

What do organizational effects of hormones lead to?

Answer 17

Major, generally irreversible aspects of sexual differentiation.

Question 18

What is the role of AMH in male differentiation?

Answer 18

AMH causes the degeneration of Müllerian ducts, preventing the development of female reproductive structures.

Question 19

What are the consequences of hormonal exposure during pregnancy or the estrus cycle?

Answer 19

Sex-specific hepatic steroid metabolism may be required.

Question 20

What is the significance of the genital/gonadal ridge?

Answer 20

It is a bipotential tissue that can differentiate into either ovaries or testes.

Question 21

True or False: The presence of the W sex chromosome in birds leads to male differentiation.

Answer 21

False

Question 22

What is the effect of testosterone on the development of the Wolffian ducts?

Answer 22

Testosterone stimulates the development of the Wolffian ducts into male reproductive structures.

Question 23

What is the role of the liver in sex differentiation?

Answer 23

The liver metabolizes steroids differently in males and females, affecting overall metabolism.

Question 24

What is the role of testosterone during development?

Answer 24

Masculinization/defeminization

Testosterone plays a crucial role during a specific time in development known as the critical period.

Question 25

What is meant by the term 'critical period' in development?

Answer 25

A specific time in development when significant changes occur ## Footnote During these periods, such as prenatal development and puberty, organizational effects of hormones take place.

Question 26

What is an organizational effect of hormones?

Answer 26

A permanent change in the nervous system and behavior ## Footnote This effect leads to major, generally irreversible, aspects of cell and tissue differentiation.

Question 27

During which developmental stages do organizational effects of hormones typically occur?

Answer 27

Prenatal development and puberty ## Footnote These are critical periods for hormonal influence on development.

Question 28

What is a freemartin?

Answer 28

An infertile female mammal with masculinized behavior and non-functioning ovaries ## Footnote Freemartins typically result from prenatal exposure to male hormones.

Question 29

How does a freemartin acquire male characteristics?

Answer 29

By exchange of cellular material from a male twin in utero ## Footnote This occurs via vascular connections between placentas.

Question 30

What genetic composition does a typical freemartin have?

Answer 30

Sterile XX/XY ## Footnote Originally XX, the freemartin acquires the male (XY) component during development.

Question 31

What modifications occur to the ovaries of a freemartin?

Answer 31

They develop testes-like structures ## Footnote These structures can be retained in the abdomen.

Question 32

What area of the brain is masculinized in freemartins due to exposure to androgens?

Answer 32

Hypothalamus ## Footnote This masculinization leads to male patterns of behavior.

Question 33

True or False: Freemartinism is an example of organizational effects of hormones.

Answer 33

True ## Footnote The condition illustrates how hormonal exposure can lead to permanent changes in development.

Question 34

What are the three types of sex that each individual has?

Answer 34

Genetic sex, gonadal sex, phenotypic sex ## Footnote These characteristics help define the sexual differentiation in mammals.

Question 35

What would be the genetic, gonadal, and phenotypic sex of an XY mouse with an inactivating mutation of the SRY gene?

Answer 35

Genetic sex: XY, Gonadal sex: female, Phenotypic sex: female ## Footnote The SRY gene is crucial for male development; its inactivation leads to female characteristics.