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
2
Q
In mammals which chromosome determines sex?
A
Y
3
Q
Female chromosome =
A
XX
4
Q
Male Chromosome =
A
XY
5
Q
Since females are XX, all oocytes carry a __ chromesome
A
X
6
Q
Males are XY, so sperm can carry ?
A
Sperm can carry an X or a Y chromosome
7
Q
What determines the sex of the embryo?
A
Sperm content
8
Q
Formation of ovaries or testes is an ____ process?
A
active gene-directed process (no default state
9
Q
early embryonic gonad is?
A
bi- potential
10
Q
When can sex differentiation occur?
A
week 7 of development
11
Q
What are the 2 systems of ducts?
A
wolffian - male
mullerian - female
12
Q
What is the development of male duct dependent on?
A
hormones
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
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
15
Q
___ is a testis determining factor?
A
SRY gene
16
Q
Testis determination factor protein:
A
- encoded by SRY gene
- testicular development: Sertoli and Leydig cell proliferation
- activates SOX-9 gene
17
Q
SOX- 9: sertoli cells
A
- induce steroidogenic factor 1 (Sf1)
- upregulate anti-mullerian hormone (AMH)
18
Q
SOX- 9: Leydig cells
A
- induce steroidogenic factor 1 (Sf1)
- increases testosterone production
19
Q
What happens to XX humans with extra copy of SOX-9 gene?
A
they develop as males despite SRY absence
20
Q
In humans, SRY and SOX-9 genes stimulate:
A
the bipotential gonad to form testis
21
Q
What 2 hormones does the testis produce?
A
-Testosterone
-Anti-mullerian hormone
22
Q
Testosterone:
A
- forms external male penis from urethral folds
- wolffian duct becomes the internal male reproductive system (epididymis, vas deferens
23
Q
anti-mullerian hormone:
A
degeneration of mullerian duct
24
Q
What do females not have that males do?
A
Y chromosome (SRY gene )
25
What are the 2 ovary determining factors?
-DAX1 gene
-WNT4 gene
26
DAX1 gene:
Identified in XY females
- normal Y chromosomes
- duplication in the DAX1 region of the X chromosome
27
DAX 1 gene disrupts?
SRY function
- dysfunctional testis
28
DAX1 down-regulates:
Testis Sf1 expression
- testis can't produce teststerone
- mullerian ducts predominate
29
WNT4 gene:
- expressed in bi-potential gonad
- undetectable in the XY gonad
- maintained in XX gonad
- XX WNT4 knock-out mice have abnormal ovaries
30
__ and __ stimulate bi-potential gonad to form an ovary
DAX1 and WNT4
31
Ovary produces?
Estrogen
32
Estrogen acts on which duct?
Mullerianduct
- development of uterus, oviducts, and cervix
33
Fertilization with X/Y sperm determines?
Sex of offspring
34
What determines sex in reptiles?
- Genotypic Sex
- Also thermosensative period of development
35
Australian skink:
- male
- female
Males: XY
Females: XX
- low temp: genotypic XX females become phenotypic males (XX males)
36
Australian dragon lizard:
Male:
Female:
Male: ZZ
Female: ZW
- High temp: genotypic ZZ males become phenotypic females (ZZ females)
37
High temperature increases:
Aromatase
- converts androgens to estrogens
- biased sex ratio towards females
38
Parents can maximize their reproductive fitness by?
By biasing birth set ratio in favor of the gender with the greatest potential to outperform its peers
39
Sex allocation hypothesis:
- dominant males father most offspring
- subordinate males do not mate
- All females will get pregnant
40
Only females with high rank/body condition will produce?
Produce males which join the dominant reproducing males
41
Mules born to nutritionally restricted mothers are?
Are smaller as adults than males born to mothers with good body condition
42
Females - with good condition should  off to produce?
Male offspring
43
Females with poor condition should opt to produce?
Female offspring
44
Adaptive control of gender bias:
- 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
Fig wasp population density = low, get bias in favor of
In favor of males:
- disperse to fertilize females in other colonies
- maximize genetic potential
- minimize inbreeding
46
Ruff food availability = poor, sex bias in favor of
In favor of females :
- maximize offspring production
- don't waste food on multiple males ( need 1 to fertilise)
- cost to the mothers
47
Red deer __ correlates with offspring ratio
maternal condition correlates offspring sex ratio
48
Red deer dominant females have more __ offspring
Male - dominate correlate with testosterone concentration
49
Red dear set bias is eliminated with
High population density:
- nutritional stress
- increased confrontation to maintain dominant position
- all males will have the chance to mat
50
American opossum ___ correlates ?
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
Non-human primates ____ correlates offspring sex ratio
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
Humans show __ control of gender bias?
- Socioeconomic variables ( famine)
- environmental stressors
- psychological stress
53
Pre-conception nutrition: maternal diet high in fats saturated or glucose =
Increased males born
54
Pre-conception nutrition: Maternal diet high in omega-6 polyunsaturated fatty acids(vegetable oils ) =
Increased females horn
55
Human change in nutritional status: gaining =
Produce sons
56
Human change in nutritional status: losing condition =
Produce daughters
57
Environmental stressors in humans : exposure of to makes endocrine disrupters:
Skews set ratio in offspring
58
How might mothers influence the sex of their children? (pre- and post-conception)
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
Female reproductive tract might control?
Gender bias:
- sex specific sperm selection progression?
- set specific fertilization?
- set specific embryo implantation / survival
60
When is it less costly for female to manipulate gender bias?
Less costs Before/at fertilization compared to later during pregnancy
61
Female tract is?
Female tract is selective not passive - controls sperm progression
Ex: 30 billion sperm inseminated but only 1000-5000 reach oviduct
62
Cervix:
Mucus removes DNA damaged sport
63
Uterus:
Immunological ( neutrophils) removal of membrane damaged sperm
64
Utero tubal junction:
- prevents 90% of sperm in uterus passing into oviduct
- restricts entry to minimize polyspermy
- opportunity to exercise choice
65
True or false: the female will select sperms from a particular male
True
66
Female tract can select out a sperm with pour septic integrity using?
CD52
67
Morphology difference between X and Y sperm?
X sperm: increased head, mid piece and tail length
68
Sperm morphology reflects ?
DNA integrity
69
Set determined by?
Chromosomes
70
Offspring gender influenced by?
Environment:
- temp, dominate, nutrition, toxins, psychological stress
71
Mothers manipulate off spring sex by?
Sperm selection:
- prosnession at UTJ and oviduct
72
Females select sperm by?
Genetic profiling
- surface makers
73
How do X and Y sperm differ?
- Morphology, protein expression microRNAs
74
X and Y sperm induce?
Sex specific gene expression in the female tract
