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#1: SoR > Lecture 1 > Flashcards

Lecture 1 Flashcards

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1
Q

What is sexual determination?

A

Genetically controlled process dependent on ‘switch’ on Y chromosome

Chromosomal determination of male or female.

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2
Q

What is sexual differentiation?

A

Process by which internal and external genitalia develop as male or female

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3
Q

Describe the relationship between sexual determination and differentiation

A

The two processes are contiguous and consist of several stages

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4
Q

Which gene is responsible for testicular formation?

A

SRY gene

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5
Q

What is the SRY gene?

A

Gene found on the short arm of the Y chromosome that creates the testes.

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6
Q

What happens in the absence of the Y chromosome?

A

Development of ovaries

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7
Q

When does the SRY gene produce its effects?

A

Switches on briefly during embryo development (>week 7) to make gonad into a testis

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8
Q

Name the testicular cells and their hormone secretions

A

Sertoli cells: AMH

Leydig cells: Testosterone

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9
Q

What are the effects of testicular hormone release?

A

Products of testis influence further gonadal and phenotypic sexual development

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10
Q

Describe the structure and function of SRY gene

A

SRY is a DNA binding protein that acts as a transcription factor

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11
Q

What transcription factors are responsible for testis formation?

A

SRY and SOX9 are TF that turn OFF genes promoting ovarian development, leading to testicular formation

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12
Q

Where does DNA bind during testis formation?

A

Critical site of DNA binding is upstream of SOX9

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13
Q

How is SOX9 activated?

A

SOX9 can bind own upstream activation site = levels remain high even if SRY declines.

+ve feedback mechanism.

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14
Q

What are the effects of SOX9 activation?

A

SOX9 acts to stimulate expression of further downstream genes ==> become Sertoli cell

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15
Q

Describe the relationship between SRY and SOX9

A

SRY determines executive policy and SOX9 implements it

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16
Q

What are the 4 mechanisms of SOX9 action?

A
  1. PDG2 production
  2. FGF9 production
  3. AMH production
  4. Female TF WNT4 / FOXL2 inhibition
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17
Q

How does SOX9 stimulate PDG2 secretion?

A

Via pre-sertoli cells

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18
Q

What is the effect of SOX9 PGD2 secretion?

A

PGD2 acts as a paracrine hormone to stimulate further SOX9 production in pre-sertoli cells

2nd +ve feedback ensures all precursor cells commit to sertoli cell pathway

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19
Q

What are the effects of SOX9 FGF9 production?

A

Acts as a chemotactic factor for cell migration into developing testis.

Further stimulates SOX9 production

3rd +ve feedback mechanism

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20
Q

Describe the effects of SOX9 AMH production

A

Causes regression of mullerian ducts which develop into uterus and fallopian tubes in females

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21
Q

What occurs in the absence of SRY gene?

A

WNT4 and FOXL2 are stimulated.

FOXL2 inhibits SOX9

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22
Q

What happens after fertilisation in gonadal development?

A

A pair of bipotential gonads develop.

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23
Q

What is the precursor of bipotential gonads derived from? Where is this and when does it happen?

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A

Precursor = Common somatic mesenchymal tissue precursors called genital ridge primordia

Where = posterior wall of lower thoracic lumbar region

When = between 3.5 and 4.5 weeks

24
Q

Gonadal development in females

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A

Uterine tubes, uterus and upper third of vagina

25
Gonadal development in males
Vas deferens, prostate and seminal vesicles
26
What are bipotential?
Internal genitalia and gonads
27
3 waves of cells invading the genital ridge
1. Primordial germ cells - become sperm or oocytes 2. Primitive sex chords - become Sertoli cells or Granulosa cells 3. Mesonephric cells - become blood vessels, Leydig cells or Theca cells
28
Primordial germ cell migration
An initially small cluster of cells in the epithelium of the yolk sac expands by mitosis at around 3 weeks. They then migrate to the connective tissue of the hind gut, to the region of the developing kidney and on to the genital ridge – completed by 6 weeks.
29
Primitive sex cords
Cells from the germinal epithelium that overlies the genital ridge mesenchyme migrate inwards as columns called the primitive sex cords. In females, it leads to no SRY. The sex cords are ill defined and do not penetrate deeply but instead condense in the cortex as small clusters around primordial germ cells – precursor of ovarian follicle. They eventually become Granulosa cells.
30
Primitive sex cords in males
SRY expression Penetrate medullary mesenchyme & surround primordial germ cells to form testis cords – precursor of seminiferous tubules. Eventually become Sertoli cells which express AMH.
31
Primitive sex cords in females
No SRY Sex cords are ill defined and do not penetrate deeply but instead condense in the cortex as small clusters around primordial germ cells – precursor of ovarian follicle. Eventually become Granulosa cells.
32
Mesonephric cells
These originate in the mesonephric primordium which are just lateral to the genital ridges.
33
What do male mesonephric cells produce?
Act under the influence of pre-sertoli cells (which themselves express SRY) to form: 1. Vascular tissue 2. Leydig cells (synthesize testosterone, do not express SRY) 3. Basement membrane – contributing to formation of seminiferous tubules and rete-testis
34
What do female mesonephric cells produce?
Without the influence of SRY they form: 1. Vascular tissue 2. Theca cells.
35
Mullerian ducts
- Internal reproductive organ - Most important in females - Inhibited in the male by AMH. -Leads to internal sexual differentiation into female genitalia = uterine tubes, uterus and upper third of vagina
36
Wolffian ducts
- Internal reproductive organ - Most important in males - Stimulated by testosterone. - Lack of stimulation by testosterone = regression in females. -Leads to internal sexual differentiation into male genitalia = prostate, vas deferens and seminal vesicles
37
External differentiation in males
Testosterone converted in genital skin to the more potent androgen dihydrotestosterone (DHT) by 5-alpha reductase. DHT binds to testosterone receptor but is more potent than testosterone.
38
Role of DHT in differentiation of male external genitalia
- Clitoral area enlarges into penis - Labia fuse and become ruggated to form scrotum - Prostate forms
39
What causes regression of Wolffian ducts in the ovary?
Lack of androgens
40
Effects of lack of androgen in the ovary
Formation of vagina, labia and clitoris
41
What is gender classification and how are gender attributes assigned?
The bipolar physiological classification of male or female is paralleled by bipolar allocation of psychosocial traits or gender attributes. Gender attributes are based on attitudes, expectations, behaviours or roles which may be highly complex.
42
Gender identity
Self-representation or identification as male or female (or neither). 
43
Gender role
Expression or portrayal of psychological characteristics that are considered sexually dimorphic within the general population (eg. toy preferences / physical aggression etc). 
44
Sexual orientation
Refers to choice of sexual partner and erotic interest (eg. include heterosexual, bisexual, homosexual).
45
Name for individuals who feel their own gender identity is different to that of their assigned gender?
Transgender or non-binary
46
Psychosexual neutrality
The view that gender assignment of a newborn with ambiguous genitalia can be made regardless of the endocrine history.
47
Neural bias
The idea that a tendency for male or female is already present in neonates as a result of prenatal factors such as the hormonal milieu in utero.
48
Relationship between sex hormones and behaviour in animals
Exposing animals to sex hormones during a critical period before or just after birth is associated with sexually divergent behaviour.
49
Gender difference in the brain?
Many genes are differentially expressed in male and female embryonic brains Morphological and functional differences in human brain structure described according to sex Neuroimaging shown functional sex differences in a variety of brain regions when subjects have undergone activities related to emotion, memory, learning, language, olfaction, vision, hearing, navigating, processing of faces and pain perception.
50
How does amygdala size differ in females and males?
Amygdala is larger in males and size is positively correlated with aggressive behaviour across species (Males have bigger heads)
51
Role of amygdala
Brain region involved in emotional processing
52
Which side of amygdala is more active in males and females
Females = left amygdala = associated with emotional memories Males = right amygdala = associated with action
53
How does the hippocampus differ in females and males?
Hippocampus contains more grey matter in females - involved in memory & social cognition.
54
What is social learning?
The phenomenon that we may develop ideologies of gender assigned at birth. Some gendered patterns of behaviour may be induced by the way boys and girls are treated or as a result of the expectations of others.
55
What is differentiation of human brain due to?
Hormonal environment in utero or neonatally

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