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NEUR454 > Lecture 3 > Flashcards

Lecture 3 Flashcards

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1
Q

sexual differentiation

A

The process by which individuals develop the characteristics associated with being male or female

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2
Q

the primary step in sexual differentiation occurs at

A

fertilization

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3
Q

sex determination

A

The point at which an individual begins to develop as either a male or a female.

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4
Q

main event in sex determination

A

fusion of egg and sperm

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5
Q

In mammals, chromosomal sex:

A

homogametic sex (XX) is female
heterogametic sex (XY) is male

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6
Q

Describe the steps from chromosomal sex to behavioural sex

A

chromosomal sex -> gonadal sex -> hormonal sex -> morphological sex -> behavioural sex

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7
Q

Sexual Differentiation

A

The developmental process of becoming male or female.

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8
Q

__ is fundamental during sexual differentiation and determines __

A

CHROMOSOMAL SEX is fundamental during sexual differentiation and determines GONADAL SEX

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9
Q

chromosomal sex

A

The sex of an individual as determined by the sex chromosomes that an individual receives at fertilization.

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10
Q

homogametic sex

A

The sex that has two similar sex chromo- somes. Except for birds and some reptiles, female vertebrate animals are the homogametic sex because they have two X chromosomes.

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11
Q

gonadal sex

A

The sex of an individual as determined by the possession of either ovaries or testes. Females have ovaries, whereas males have testes.

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12
Q

gametic sex

A

The sex of an individual as determined by the production of ova by females and sperm by males.

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13
Q

hormonal sex

A

The sex of an individual as determined by the concentration of androgens and estrogens. Males tend to have higher androgen concen- trations, while females tend to have higher estrogen concen- trations.

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14
Q

morphological sex

A

The sex of an individual as determined by body form.

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15
Q

behavioral sex

A

The sex of an individual as discriminated on the basis of male-typical and female-typical behaviors.

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16
Q

gender identity

A

The psycho- logical self-perception of being either male or female.

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17
Q

Chromosomal sex* is fundamental during sexual differentiation and determines

A

gonadal sex

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18
Q

SRY gene:

A

Sex-determining region of the Y chromosome; the gene that is responsible for the transformation of the undifferentiated gonad into a testis.

SRY gene, gives rise to SRY protein (SRY protein also referred TDF-testis determining factor), SRY protein binds to SF-1: they form a transcription factor that regulates the transcription of the SOX9 gene

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19
Q

The primary step in the process of mammalian sexual differentiation occurs at

A

fertilization

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20
Q

ovum can be fertilized by a sperm bearing either an X or a Y chromo- some (FIGURE 3.8). This event, called

A

sex determination

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21
Q

germinal ridge

A

A thickened ridge of tissue on the ventrome- dial surface of each mesoneph- ros of an embryo that has the potential to develop into either a testis or an ovary.

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22
Q

. In most mammals studied to date, whether the germinal ridge will develop into a testis or an ovary is determined by

A

the cellular expression of a gene known as SRY (sex-determining region on the Y chromosome

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23
Q

When the protein products of these two genes (SRY and SOX9)
are produced:

A

the middle (medulla) of the germinal ridge devel-
ops and a testis forms

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24
Q

If products of the SRY or
SOX9 genes are not produced, or the genes are not expressed in
the required sequence, then

A

the outer part of the germinal ridge
(the cortex) develops and an ovary is formed

*in some cases
neither testes nor ovaries are formed.

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25
__ differentiate the gonads
genetic influences (SRY, SOX9, WNt4)
26
what is the testis determining factor
SRY gene -> SRY protein binds with SF-1 -> activates transcription SOX9 -> undifferentiated gonad develops into testis
27
If the SRY gene is expressed and the testis determination factor protein is present;
the medulla of the germinal ridge develops, forming a testis
28
If no SRY gene is expressed and testis determination factor is not present,
the cortex of the protogonad develops, and an ovary is formed. *wnt4 is inhibiting SOX9
29
Although it is generally as- sumed that the ovaries are formed in the absence of active gene regulation, more recent lines of evidence suggest that
expression of a gene called Wnt4 (wingless-related MMTV integration site 4) is required for normal ovarian development
30
__ required for typical ovarian development
Wnt4
31
Aside from gonad differentiation, other sexual differentiation mainly reflects:
hormonal mediation
32
hormonal secretions from developing gonads determine:
whether male or femaledevelop
33
the prevailing hypothesis about the initiation of sexual differentiation indicates that
the gonads are differentiated by genetic influences (SRY and SOX9) and that all other sexual differentiation reflects hormonal mediation
34
anlagen:
The primordial sub- strate in a developing individual Bipotential gonad
35
accessory sex organ
The internal organs of the male and female reproductive tract that connect the gonads to the external environment.
36
Müllerian duct system
A duct system present in both sexes during embryonic development that connects the gonads to the exterior. During normal develop- ment, the Müllerian duct system develops into the accessory sex organs in females and regresses in males.
37
Wolffian duct system
A duct system present in both sexes during embryonic development that connects the gonads to the exterior. During normal development, the Wolffian duct system develops into the accessory sex organs in males and regresses in females.
38
Müllerian inhibitory hormone (MIH)
A peptide hormone produced in the Sertoli cells in the developing testis that suppresses development of the Müllerian duct system, which prevents development of the uterus and cervix. Also called Müllerian inhibitory factor (MIF)
39
Male development of the accessory sex organs re- quires two products from the embryonic testes:
testosterone and a peptide hormone called Müllerian inhibitory hormone (MIH)
40
Male development of the accessory sex organs re- quires two products from the embryonic testes: testosterone and a peptide hormone called Müllerian inhibitory hormone (MIH). Testosterone is necessary to __ and MIH is necessary to __
Testosterone is necessary to stimulate Wolffian duct development. Müllerian inhibitory hormone, as its name implies, causes the regression of the Müllerian duct system.
41
The Müllerian and Wolffian duct systems are normally both
present early in embryonic development
42
testicular hormones:
testosterone and MIH
43
In the absence of testicular hormones, the Müllerian duct system develops into
the fallopian tubes, uterus, and upper vagina, (while the wolfian duct regresses)
44
When testicular hor- mones are present, as is normally the case in male mammals, the Wolffian ducts eventually develop into
into the seminal vesicles and vas deferens, and the Müllerian ducts regress
45
masculinization
The induction of male traits *Wolffian duct development
46
feminization
the induction of female traits *mullerian duct development
47
demasculinization
The removal of the potential for male traits. *wolffian duct regression
48
defeminization
the removal of the potential for female traits *mullerian duct regression
49
COUP-TFII
Internal differentiation Wolffian duct regression factor in females
50
sexual differentiation of the accessory sex organs proceeds along two continua
(1) a masculinization-demasculinization scale and (2) a feminization-defeminization scale (
51
genital folds
A fold of skin on each side of the genital tubercle that develops into the labia mi- nora in females and the urethral groove and scrotum in males.
52
genital tubercle
The region of the embryo that develops into male or female genitalia.
53
the __ and __ are common to both sexes and develop into the external genitalia
The genital tubercle and genital folds
54
females: what develops from genital tubercle and genital folds in females?
clitoris and vaginal labia
55
males: what develops from genital terbicle and genital folds?
genital tubercle: penis genital fold: scrotal sac (eventually contains testes)
56
Prader scale
for scoring degrees of genital virilization The Prader scale is a scoring system for grading the degrees of genital masculinization. The Prader scale starts at 0, which is an unvirilized female, and ends at 5, which is a completely virilized female (a female who appears externally male at birth with the labial/scrotal sac empty since there are no testicles).
57
_are responsible for the differentiation of the external genitalia
androgens (testosterone -> reductase-> 5-a dihydrotestosterone - DHT)
58
In the absence of DHT (an androgen)n:
a clitoris develops from the genital tubercle, and the vaginal labia develop from the genital folds.
59
In the presence of DHT (an androgen):
the genital tubercle develops into a penis, and the genital folds fuse into the scrotum
60
What is important for external organ differentiation?
5a-dihydrotestosterone (DHT)
61
5α-dihydrotestosterone (DHT)
main androgenic metabolite of testosterone
62
An enzyme nec- essary to convert testosterone to 5􏰁-dihydrotestosterone.
5a-reductase
63
where is 5a reductase present
locally abundant in the embryonic genital skin of both females and males
64
If unusually high concentrations of androgens are available to a female fetus, then
DHT conversion in the genital skin occurs, and the development of male- typical external genitalia proceeds.
65
Males that congenitally lack the 5a-reductase enzyme
undergo incomplete differentiation of the external genitalia and may be considered female at birth
66
Females that lack 5a-reductase have
female-typical external genitalia because typical female genital development occurs in the absence of sex steroid hormones.
67
SRY protein activates
the expression of SOX9
68
SOX9 drives
Sertoli cell differentiation
69
SRY protein activates the expression of SOX9. SOX9 drives Sertoli cell differentiation, which leads to:
many things but importantly secretion of mullerian inhibiting hormone
70
If SRY is absent or nonfunctional
SOX9 is not upregulated → gonad develops into an ovary.
71
strategies to study human behavioral sex differences (4):
1. Animal Models 2. Human/animals having undergone anomalous sexual differentiation 3. Fluid samples from routine amniocentesis 4.observing common behaviours in children among different cultures
72
what is turner syndrome:
a congenital lack/damage to second chromosome xo
73
4 characteristics of Turner Syndrome
(1) unambiguously sexed as girls at birth (2) not fully developed ovaries (3) lack of steroid hormones prenatally/postnatally (4) exogenous hormonal treatment needed to induce puberty
74
Swyer syndrome (5):
(1) chromosomal (xy) male, biological female (female external and internal organs) (2) gonadal streaks instead of sex glands (gonadal streaks = fibrous nonfunctional tissue) (3) in only 15-20% of cases is there SRY mutation (4) breasts do not form properly Since the gonads don’t produce estrogen (a hormone needed for breast development), the breasts don’t develop normally at puberty without hormone treatment. (5) need exogenous hormonal treatment to induce puberty
75
androgen insensitivity syndrome:
(1) individual is genetically XY, but there is a mutation on X chromosome (2) Testes develop (testosterone and MIH) (3) no function androgen receptors (4) female appearance and regard themselves as female
76
What happens to females XX with androgen insensitivity syndrome?
Genetic XX females with this mutation have a second X chromosome that contains the normal gene for androgen receptors, so they suffer no ill effects from this condition
77
5α-reductase
5α-reductase is an enzyme that converts testosterone into a more potent androgen called dihydrotestosterone (DHT). is essential for the development of male external genitalia
78
5a-reductase deficiency (5):
1.Genetic XY, mutation on chromosome 2 2. At birth, born with ambiguous external organs and undescended testes 3. usually considered female 4. At puberty, increase in levels of androgens activate receptors 5.Because of changes at puberty, some individuals may take on male-gender identity
79
Anomalous sexual differentiation in women usually results from:
prenatal exposure to androgens (exogenous or endogenous)
80
Anomalous sexual differentiation in women usually results from prenatal exposure to androgens, this leads to:
masculinization of reproductuve function and subsequent behaviour
81
congenital adrenal hyperplesia
A genetic deficiency that results in the overproduc- tion of androgens by the adrenal glands. This syndrome has no reported effects on genital dif- ferentiation in males but causes various degrees of masculin- ization of the external genitalia in females, which may lead to erroneous assignment of sex at birth.
82
Turner syndrome
A congenital condition in which individuals lack an X chromosome (XO). These individuals have a female external appearance, but ovarian development is usually limited, and they do not attain puberty without medical atten- tion.
83
which enzyme is necessary for the production of mineral corticoids (aldosterone) and glucocorticoids (cortisol) in the adrenal glands
21 - hydroxylase
84
individuals with congenital adrenal hyperlasia lack __, resulting in __
Individuals with CAH lack 21-hydroxylase, resulting in overproduction of adrenal androgens, the only pathway available in the absence of this enzyme
85
does congenital adrenal hyperplasia affect males ?
not really
86
what disorder results in severe masculinization of the genitalia in affected females
Congenital Adrenal Hyperplesia
87
androgen insensitivity (AIS)
A condition in genetic males, in which functional androgen receptors are absen
88
androgen insensitivity (AIS) caused by:
genetic mutation on the X chromosome.
89
XY individuals with andorgen insensitivity syndrome have what appearance
per- fectly normal-appearing female external genitalia and are sexed and reared as girls.
90
Why are XY individuals with androgen insensitivity sterile ?
r, in genetic XY males, because a Y chromosome is present, the SRY gene is activated and testicular development proceeds, accompanied by significant prenatal and postnatal androgen secretion. The testes also produce MIH, which causes the regression of the Müllerian duct systemthe Müllerian ducts failed to develop in these individuals, there are no uteri or fallopian tubes, and they are sterile.
91
MIH formed from
sertoli cells (testes)
92
testosterone formed from
leydig cells
93
93
what does wnt4 do?
inhibit SOX9 in females for gonadal differentiation

NEUR454 (7 decks)

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