Lecture 19

Question 1

What is the definition of sex at an anatomical level?

Answer 1

Gonadal: internal genitalia (ovaries/testes)
Morphological: external genitalia

Question 2

What is sex at the chromosomal level?

Answer 2

Defined based on the presence of XX or XY chromosomes in somatic cells

Question 3

What is the difference between X and Y chromosomes? What are the similar structures?

Answer 3

Size and genetic material; 2 pseudoautosomal regions

Question 4

How does SRY gene expression influences hormone production/ sex determination?

Answer 4

It initiates male sex development; if the SRY gene is +, leads to testes determining factor (TDF,SOX9+), if SRY-, no TDF (SOX9-)

Question 5

How is testosterone produced in a fetus?

Answer 5

Testosterone is produced by leydig cells

Question 6

How is estrogen produced in a fetus?

Answer 6

Estrogens are produced by follicular cells

Question 7

What is chromosomal aneuploidy?

Answer 7

An abnormal number of chromosomes in a cell

Question 8

What is dosage compensation?

Answer 8

Ensures that XY males and XX females express the same amount of X chromosome— one of the two X chromosomes is inactivated (XCI)

Question 9

What is a Barr body?

Answer 9

Dense heterochromatic structure formed by XCI in XX females

Question 10

How do the levels of SHOX gene in the pseudo-autosomal region compare with each other?

Answer 10

They have comparable levels of SHOX gene

Question 11

Where does sex development begin? What morphological/gonadal sex does it begin expressing?

Answer 11

The bipotential urogenital ridge at 6 weeks of gestational age; both male and female at the same time

Question 12

What are Mullerian and Wolffian ducts?

Answer 12

Ducts located in the urogenital ridge that differentiate into female or male structures at week 7

Question 13

What develops from a SOX9- gene?

Answer 13

Ovaries— germ cells develop oocytes, granulosa cells do not produce AMH and Müllerian ducts develop and wolffian ducts degrade
Testes— germ cells develop sperm; Sertoli cells produce AMH and wolffian ducts develop

Question 14

What does the development of external genitalia depend on?

Answer 14

Androgens and estrogens

Question 15

What produced androgens?

Answer 15

Leydig cells

Question 16

What produces estrogen?

Answer 16

Follicular cells

Question 17

What time are male and female external genitalia first visible by ultrasound?

Answer 17

11 weeks

Question 18

How many types of estrogens exist? What are they?

Answer 18

E1. Estrone
E2. Estradiol
E3. Estriol

Question 19

What turns testosterone into estrogen?

Answer 19

Aromatase

Question 20

What is the function of testosterone? What is the function of estrogen?

Answer 20

Testosterone: promotes protein synthesis, increases bone density and muscle mass, male sex organ development
Estrogen: important for bone health

Question 21

How are steroids synthesized?

Answer 21

Modifications of cholesterol

Question 22

What are the five stages of post-natal development?

Answer 22

1. Neonatal: birth to 1 month
2. Infancy: 1 month to 1 year
3. Childhood: 1 year to onset of puberty
4. Adolescence: puberty to when growth is completed
5. Maturity: when growth is completed

Question 23

What is the difference between organizational and activation all hormonal effects?

Answer 23

Organizational: during the critical window, while neural structures are being established
Activational: puberty occurs in puberty with a rise in hormones

Question 24

How do sex hormones affect body systems in puberty?

Answer 24

1. Hypothalamus increases GnRH— FSH and LH
2. Gamete production initiated
3. Sex hormones are released and secondary sex characteristics and behaviour
4. Accelerated growth rate