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Reproduction > 2.6 The Mysteries of Sex Determination Pt.1 > Flashcards

2.6 The Mysteries of Sex Determination Pt.1 Flashcards

1
Q

Sex determination refers to?

A

the development of characteristics which allow an individual to be identified as male or female

  • reproductive system: testis vs. ovaries
  • external phenotype
  • behavior: hormone induced
  • metabolism
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2
Q

In mammals which chromosome determines sex?

A

Y

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3
Q

Female​ chromosome =

A

XX

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4
Q

Male Chromosome =

A

XY

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5
Q

Since females are XX, all oocytes carry a __ chromesome

A

X

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6
Q

Males are XY, so sperm can carry ?

A

Sperm can carry an X or a Y chromosome

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7
Q

What determines the sex of the embryo?

A

Sperm content

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8
Q

Formation of ovaries or testes is an ____ process?

A

active gene-directed​ process (no default state

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9
Q

early embryonic gonad is?

A

bi- potential

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10
Q

When can sex differentiation​ occur?

A

week 7 of development

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11
Q

What are the 2 systems of ducts?

A

wolffian - male
mullerian - female

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12
Q

What is the development of male duct dependent on?

A

hormones

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13
Q

Which duct phenotype is the default?

A

female duct phenotype
- predominates in the absence of fetal testis
- remove bi-potential gonads, the ​female reproductive system develops

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14
Q

How to make a male?

A

The Y chromosome determines male sex

SRY gene:
- 140 kb sex-determining​ region on Y chromosome
- encodes transcription factors that activate testis formation

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15
Q

___ is a testis determining factor?

A

SRY gene

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16
Q

Testis determination factor protein:

A
  • encoded by SRY gene
  • testicular development: Sertoli and Leydig cell proliferation​
  • activates SOX-9 gene
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17
Q

SOX- 9: sertoli cells

A
  • induce steroidogenic​ factor 1 (Sf1)
  • upregulate anti-mullerian hormone (AMH)
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18
Q

SOX- 9: Leydig​ cells

A
  • induce steroidogenic​ factor 1 (Sf1)
  • increases testosterone production
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19
Q

What happens to XX humans with extra copy of SOX-9 gene?

A

they develop as males despite SRY absence

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20
Q

In humans, SRY and SOX-9 genes stimulate:

A

the bipotential gonad to form testis

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21
Q

What 2 hormones does the testis produce?

A

-Testosterone
-Anti-mullerian hormone

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22
Q

Testosterone:

A
  • forms external male penis from urethral folds
  • wolffian duct becomes the ​internal male reproductive system (epididymis, vas deferens
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23
Q

anti-mullerian hormone:

A

degeneration​ of mullerian duct

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24
Q

What do females not have that males do?

A

Y chromosome (SRY gene )

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25
Q

What are the 2 ovary determining factors?

A

-DAX1 gene
-WNT4 gene

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26
Q

DAX1 gene:

A

Identified in XY females
- normal Y chromosomes
- duplication in the DAX1 region of the X chromosome

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27
Q

DAX 1 gene disrupts?

A

SRY function
- dysfunctional testis

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28
Q

DAX1 down-regulates:

A

Testis Sf1 expression
- testis can’t produce teststerone
- mullerian ducts predominate

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29
Q

WNT4 gene:

A
  • expressed in bi-potential gonad
  • undetectable in the XY gonad
  • maintained in XX gonad
  • XX WNT4 knock-out mice have abnormal ovaries
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30
Q

__ and __ stimulate bi-potential gonad to form an ovary

A

DAX1 and WNT4

31
Q

Ovary produces?

A

Estrogen

32
Q

Estrogen acts on which duct?

A

Mullerianduct
- development of uterus, oviducts, and cervix

33
Q

Fertilization with X/Y sperm determines?

A

Sex of offspring

34
Q

What determines sex in reptiles?

A
  • Genotypic Sex
  • Also thermosensative period of development
35
Q

Australian skink:
- male
- female

A

Males: XY
Females: XX
- low temp: genotypic XX females become phenotypic males (XX males)

36
Q

Australian dragon lizard:
Male:
Female:

A

Male: ZZ
Female: ZW
- High temp: genotypic ZZ males become phenotypic females (ZZ females)

37
Q

High temperature increases:

A

Aromatase
- converts androgens to estrogens
- biased sex ratio towards females

38
Q

Parents can maximize their reproductive fitness by?

A

By biasing birth set ratio in favor of the gender with the greatest potential to outperform its peers

39
Q

Sex allocation hypothesis:

A
  • dominant males father most offspring
  • subordinate males do not mate
  • All females will get pregnant
40
Q

Only females with high rank/body condition will produce?

A

Produce males which join the dominant reproducing males

41
Q

Mules born to nutritionally restricted mothers are?

A

Are smaller as adults than males born to mothers with good body condition

42
Q

Females - with good condition should  off to produce?

A

Male offspring

43
Q

Females with poor condition should opt to produce?

A

Female offspring

44
Q

Adaptive control of gender bias:

A
  • known to occur in many non-mammalian species
  • occurs as response to changing environmental conditions
    Ex: food availability, temp, disease population, dersits, maternal conditions I seasons
45
Q

Fig wasp population density = low, get bias in favor of

A

In favor of males:
- disperse to fertilize females in other colonies
- maximize genetic potential
- minimize inbreeding

46
Q

Ruff food availability = poor, sex bias in favor of

A

In favor of females :
- maximize offspring production
- don’t waste food on multiple males ( need 1 to fertilise)
- cost to the mothers

47
Q

Red deer __ correlates with offspring ratio

A

maternal condition correlates offspring sex ratio

48
Q

Red deer dominant females have more __ offspring

A

Male - dominate correlate with testosterone concentration

49
Q

Red dear set bias is eliminated with

A

High population density:
- nutritional stress
- increased confrontation to maintain dominant position
- all males will have the chance to mat

50
Q

American opossum ___ correlates ?

A

maternal condition Offspring sex ratio
- increase in male off spring with high n-3 fatty acid diet
- marsupials move to the porch 14 days after conception ( mechanisms must act once before conception or on very early embryo)

51
Q

Non-human primates ____ correlates offspring sex ratio

A

maternal condition correlates offspring sex ratio
- social structure is important
Ex:
- Cologne monkey high ranking females Halle none males
- opposite is the in baboons (matriarchal society)

52
Q

Humans show __ control of gender bias?

A
  • Socioeconomic variables ( famine)
  • environmental stressors
  • psychological stress
53
Q

Pre-conception nutrition: maternal diet high in fats saturated or glucose =

A

Increased males born

54
Q

Pre-conception nutrition: Maternal diet high in omega-6 polyunsaturated fatty acids(vegetable oils ) =

A

Increased females horn

55
Q

Human change in nutritional status: gaining =

A

Produce sons

56
Q

Human change in nutritional status: losing condition =

A

Produce daughters

57
Q

Environmental stressors in humans : exposure of to makes endocrine disrupters:

A

Skews set ratio in offspring

58
Q

How might mothers influence the sex of their children? (pre- and post-conception)

A

As the female has a disproportionate role in production of offspring it is likely that most influence on offspring sex ratio is under maternal control

59
Q

Female reproductive tract might control?

A

Gender bias:
- sex specific sperm selection progression?
- set specific fertilization?
- set specific embryo implantation / survival

60
Q

When is it less costly for female to manipulate gender bias?

A

Less costs Before/at fertilization compared to later during pregnancy

61
Q

Female tract is?

A

Female tract is selective not passive - controls sperm progression
Ex: 30 billion sperm inseminated but only 1000-5000 reach oviduct

62
Q

Cervix:

A

Mucus removes DNA damaged sport

63
Q

Uterus:

A

Immunological ( neutrophils) removal of membrane damaged sperm

64
Q

Utero tubal junction:

A
  • prevents 90% of sperm in uterus passing into oviduct
  • restricts entry to minimize polyspermy
  • opportunity to exercise choice
65
Q

True or false: the female will select sperms from a particular male

A

True

66
Q

Female tract can select out a sperm with pour septic integrity using?

A

CD52

67
Q

Morphology difference between X and Y sperm?

A

X sperm: increased head, mid piece and tail length

68
Q

Sperm morphology reflects ?

A

DNA integrity

69
Q

Set determined by?

A

Chromosomes

70
Q

Offspring gender influenced by?

A

Environment:
- temp, dominate, nutrition, toxins, psychological stress

71
Q

Mothers manipulate off spring sex by?

A

Sperm selection:
- prosnession at UTJ and oviduct

72
Q

Females select sperm by?

A

Genetic profiling
- surface makers

73
Q

How do X and Y sperm differ?

A
  • Morphology, protein expression microRNAs
74
Q

X and Y sperm induce?

A

Sex specific gene expression in the female tract

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