gonads and gametes - NOT USED

Question 1

D: sex

Answer 1

the process by which a genetically novel individual is formed as the result of mixing of genes from two or more individuals

Question 2

The core elements of sex are highly conserved across virtually all eukaryotic lineages and are:

?

Answer 2

MEIOSIS – the generation of haploid gametes

SYNGAMY – the coming together of the two sets of gametic chromosomes on the same mitotic spind

Question 3

Mammals = ____ offspring, but ___ of genetic diversity

Answer 3

Mammals = few offspring, but lots of genetic diversity

Question 4

T or F

◦it’s not universal which sex is homogametic

Answer 4

T

eg, a female chick may have XY (two differnet ones)

Question 5

whats meant by dosage compensation/

Answer 5

◦X chromosome contains the majority of the genetic material, therefore in XX females one of the X chromosomes is inactivated on a random basis = forming a barr body (done at epiblast stage of development) = equalises expression of genes between members of different biological sexes

Question 6

what are barr bodies

Answer 6

Barr bodies (dense masses of chromatin seen adjacent to the nuclei, visualised using Carbol Fuschin staining)

Question 7

how did the Y chromosome evolve?

Answer 7

First step thought to be the acquisition of a male-determining gene to form a proto-Y chromosome.

Further acquisition of antagonistic mutations, aided by a series of inversions, suppresses opportunities for recombination

Lack of recombination leads to accumulation of repetitive sequences or deleterious mutations, which are then deleted

Question 8

T or F

where the X chromosome largely resembles the autosome from which it derived, and the Y chromosomes has lost most of its ancestral genes, and may instead have accumulated repetitive DNA.

Answer 8

T

Question 9

Answer 9

Question 10

D: Karyotype ..

Answer 10

Karyotype – complement of chromosomes within a cell

Question 11

describe turners syndrome

Answer 11

Turners (45XO – X usually comes from the mother due to non-disjunction from the father)

Question 12

describe Klinefelter’s syndrome

Answer 12

(47XXY – due to non-disjunction by either the mother or father)

Question 13

what is nondisjunction

Answer 13

• (Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division)

Question 14

Answer 14

Question 15

what is a persons somatic sex?

Answer 15

Somatic = penis, scrotum, prostate, vasa – vs clitoris, vagina, uterus, oviducts

Question 16

what is teh defauly state (sex wise)

Answer 16

the female

Question 17

describe SRY

Answer 17

transcription factor encoding a DNA /RNA binding protein

on Y chromosome

encodes the HMG DNa binding box

Affects the expression of a number of other genes (eg. SOX9, SOX3) involved in gonad differentiation, but precise molecular mechanisms not yet understood

Question 18

Disruption between genetic and gonadal sex = v rare (primary ___________)

Answer 18

Disruption between genetic and gonadal sex = v rare (primary hermaphroditism)

Question 19

Primary (True) Hermaphroditism:

describe

Answer 19

◦Also known as intersex

◦Can be:

◦Ovary on one side and testis on other (rare)

◦mixed ovarian testicular tissue in one or both gonads (partial or mixed gonadal dysgenesis, more common and often seen where sex chromosome mosaicism exists

Question 20

form both sexes - where do the gonads arise from?

Answer 20

the genital ridge

Question 21

what week is the genital ridge formed in?

Answer 21

5

Question 22

Genital ridges form during 5th and 6th weeks on medial side of the……

Answer 22

Genital ridges form during 5th and 6th weeks on medial side of the mesonephric ridges

Question 23

the gential ridge is colonised by?

Answer 23

Colonised by primordial germ cells migrating from the extraembryonic mesoderm close to the yolk sac.

Question 24

where do the primordial germ cells come from?

Answer 24

germ cells differentiate from the amnion as a result of wnt3A signalling from the cytotrophoblast.

This, along with chemoattractant production at the gonadal ridges, triggers the migration of the primordial germ cells (common origins of spermatozoa and oocytes) from the extraembryonic mesoderm, into the caudal part of the yolk sac, and then along the dorsal mesentery into the genital ridges.

Occurs via amoeboid movement

Question 25

at the formation of the primitive sex cords - is there male or female characteristics yet?

Answer 25

no - SRY hasnt come into play yert

Question 26

do primordial germ cells determine sex?

Answer 26

NO ## Footnote primordial germ cells are influenced by the environment they are in – they do NOT determine sex – their arrival just triggers sex specific gene expression, driving sexual differentiation

Question 27

are the gonads bipotential before SRY activation?

Answer 27

yes

Question 28

MALES: ## Footnote ◦SRY expression in the _________ cells then drives male gonadal differentiation

Answer 28

◦SRY expression in the **mesenchymal** cells then drives male gonadal differentiation

Question 29

for male developemnt: describe week 7:

Answer 29

◦WEEK 7 ◦Here, the sex cord cells proliferate, and form testis cords (Sertoli cells). Germ cells are incorporated into these

Question 30

MALE Development describe week 24

Answer 30

◦Testis cords anastomose and connect with remnants of the mesonephric tubules, the rete testis. ◦Leydig cells differentiate from mesonephric mesenchyme.

Question 31

when at what do letdig cells differentiate from?

Answer 31

◦Leydig cells differentiate from **mesonephric mesenchyme.** week 24

Question 32

◦Sertoli cells produce ...

Answer 32

◦Sertoli cells produce Müllerian Inhibiting Substance

Question 33

◦Leydig cells produce....

Answer 33

◦Leydig cells produce androgens

Question 34

Answer 34

Question 35

bascially describe how a bipotential thing differentiates into a male

Answer 35

1. SRY switched on in cells of the sex cords (sertoli cells) and in stromal cells (Leydig cells) 2. sertoli cells proliferate to form smeiniferous tubules 3. Seminiferous tubules connect with degenerating mesonephric tubules of the rete testis. 4. Androgens from Leydig cells maintain the mesonephric duct, 5. and Müllerian Inhibiting Substance from Sertoli cells stimulates degeneration of the paramesonephric duct.

Question 36

describe how a bipotential thingy turns into a female

Answer 36

1. No SRY 2. Medullary sex cords degenerate 3. Coelomic epithelium proliferates to form cortical cords 4. Cells from cortical cords surround oogonia to form primordial follicles. 5. Absence of androgens causes mesonephric duct to degenerate. 6. Absence of Müllerian Inhibiting Substance permits maintenance of the paramesonephric duct.

Question 37

Leydig cells produce what? effect?

Answer 37

Leydig cells androgens Development of penis, scrotum, vasa, accessory sex glands

Question 38

tistis produces what hormone? (its like something) effect?

Answer 38

testis Insulin like hormone 3 Gubernaculum contraction - testis descent

Question 39

what substance do sertoli cells produce?

Answer 39

sertoli cells: ## Footnote ◦Müllerian Inhibiting Substance Uterine primordium regresses in males

Question 40

what does the gonadal sex in males depend on ?

Answer 40

endocrine stuff

Question 41

androgens cause the growth of the .........

Answer 41

◦Androgens – cause growth of the mesonephric duct; eventually forming the vas deferens, epididymis and the seminal vesicles

Question 42

what does MIS do?

Answer 42

◦degrades the paramesonephric duct

Question 43

Differentiation of the external genitalia is driven primarily by ....

Answer 43

Differentiation of the external genitalia is driven primarily by **dihydrotestosterone (DHT**

Question 44

DHT is produced from ....

Answer 44

DHT is produced from **testosterone** by the activity of the **enzyme 5 alpha reductase** that is present in the local tissues

Question 45

what does absence of 5 alpha reductase lead to?

Answer 45

female genitalia

Question 46

Mesonephric duct = ..... Paramesonephric duct =..... alternative names

Answer 46

Mesonephric duct = **wolffian duct** Paramesonephric duct = **Mullerian duct**

Question 47

mesonephric duct remnant =.....

Answer 47

mesonephric duct remnant = Gartner’s cyst in wall of vagina

Question 48

Answer 48

Question 49

diference in HPG axis for men and women

Answer 49

Question 50

◦Somatic sex development involves ....

Answer 50

◦Somatic sex development involves the formation of both the internal and external genitalia

Question 51

somatic sex development is: ◦Endocrine ________ in the male, _________ in the female

Answer 51

◦Endocrine dependent in the male, independent in the female

Question 52

3 main hormones in somatic sex for males

Answer 52

◦3 main hormones 1. Androgens – stimulates development of the bipotential genital tubercle to form the glans of the penis. It also triggers fusion of the urogenital and labioscrotal folds, and development of the prostate 2. MIS – causes uterine primordium to regress 3. Insulin-like hormone 3 (INSL3) – causes the gubernaculum to shorten and the testes to descend

Question 53

INSL3 – produced by the .....

Answer 53

INSL3 – produced by the **Leydig cells**

Question 54

describe how somatic sex is hormone dependant in females

Answer 54

◦Hormone independent: * Uterus forms from the medial fusion of the inferior portion of the paramesonephric duct at the midline * Upper 1/3 of the vagina from the paramesonephric duct, lower 2/3 from the urogenital sinus * Bipotential genital tubercle bends caudally to form the clitoris * Genital swellings and urethral folds form the labia majora and minora respectively

Question 55

describe masculinisationof the brain

Answer 55

There is evidence of differences between male and female brains at various levels: Structural – e.g. size of certain areas Chemical – e.g. level of transmitters Physiological – e.g. metabolism, cyclicity Psychological – e.g. gender, aggression Cognitive – e.g. verbal fluency, spatial ability

Question 56

manifestations of Primary hermaphroditism or intersex

Answer 56

- anomalies of the gonad ## Footnote ovary on one side and testis on other (rare) mixed ovarian testicular tissue in one or both gonads (partial or mixed gonadal dysgenesis, more common and often seen where sex chromosome mosaicism exists, eg somatic loss of Y or translocation to X.

Question 57

describe the physical manifestations of secondary hermaphroditism or intersex

Answer 57

*anomalies of soma* ## Footnote **Testicular feminisation** or **Androgen insensitivity syndrome** (complete = testis + female soma 0.005%; partial = poorly developed male soma 0.01% of births) * **Congenital adrenohyperplasia** or Adrenogenital syndrome (ovary + variable somatic maleness: partial 1%, complete 0.01% of births) * **Micropenis** (poorly developed phallus 0.002%) * **Hypospadias** (urethra opens in ventral penis or in vagina 0.05-0.2% of births)

Question 58

describe congenital adrenal hyperplasia

Answer 58

CAH * XX * Deficient in **21-hydroxylase** (enzyme that converts progestogens to corticosteroids) * Results in an increase in precursors, which are then shunted down the androgen synthesis pathway * In males this results in precocious puberty * In females this causes the mesonephric duct to persist and external male genitalia to form = potentially a blind ended vagina and micropenis

Question 59

describe 5-alpha reductase deficiency

Answer 59

5-alpha reductase deficiency * XY * Known as Guevodoces * Unable to make peripheral DHT * May present with ambiguous genitalia/micropenis at birth, undergo virilization at puberty with androgen surge * But urethra often remains opening near the anus * Most are heterosexual

Question 60

describe androgen insensitivity

Answer 60

Androgen insensitivity syndrome * XY * Have normal testes and androgen production – often phenotype is less severe than textbooks suggest as some DHT may be able to bind: * Completely female = 0.005% * Poorly developed male characteristics = 0.01% * At puberty when there is a surge of androgens – secondary sexual characteristics may develop * Due to mutations in the androgen receptor in peripheral tissues

Question 61

describe Hypospadia

Answer 61

Hypospadia (urethra opens into ventral penis/vagina)

Question 62

Treatment for Congenital Adrenal Hyperplasia is generally ....

Answer 62

Treatment for Congenital Adrenal Hyperplasia is generally glucocorticoid replacement therapy, usually in the form of hydrocortisone.

Question 63

is the concept of gender learned\>

Answer 63

yess

Question 64

gender: ## Footnote ◦2 years = ◦3 years = ◦5 years = ◦7 years =

Answer 64

◦2 years = identity ◦3 years = role ◦5 years = constancy ◦7 years = policing

Question 65

D: puberty

Answer 65

◦State of transition encompassing all physiological, morphological and behavioural changes when developing from a juvenile to a fecund

Question 66

what are the effectors of puberty?

Answer 66

◦Steroids are the effectors of puberty

Question 67

D: ◦Gonadarche –

Answer 67

◦Gonadarche – level of maturation required to produce gonadal hormones

Question 68

Puberty is considered precocious if secondary sexual characteristics occur before the age of _ in girls and _ years in boys

Answer 68

Puberty is considered precocious if secondary sexual characteristics occur before the age of 8 in girls and 9 years in boys

Question 69

◦What are the main regulators of puberty and where are they produced?

Answer 69

◦GnRH - produced by neurons in the hypothalamus and released into the pituitary portal vein to the anterior pituitary ◦FSH and LH– released from the anterior pituitary in response to GnRH **◦In males** ◦Testicular androgens **◦In females** ◦Ovarian oestrogens ◦Androgens from the ovary and adrenal gland