Lect 26 Flashcards
1
Q
What is the primary purpose of sexual reproduction?
A
Creating and maintaining genetic diversity.
2
Q
When did eukaryotic sex evolve?
A
Eukaryotic sex evolved once and was present in LECA.
3
Q
How has asexual reproduction evolved in relation to sexual reproduction?
A
Asexual reproduction has evolved multiply from sexual eukaryotic species.
4
Q
What is a consequence of asexual species evolving from sexual eukaryotic species?
A
These asexual species have not evolved into other species and hence evolutionary dead-end.
5
Q
What is the cultivar of all commercial bananas?
A
Cavendish
The Cavendish banana is the most widely grown banana variety globally.
6
Q
How do Cavendish plants reproduce?
A
Asexual reproduction
Cavendish plants are sterile and do not produce seeds.
7
Q
What is true about all Cavendish banana plants?
A
They are all clones
Cloning results in genetically identical plants.
8
Q
What disease is threatening Cavendish plants?
A
Panama disease Race 4
This disease is causing significant declines in Cavendish banana populations.
9
Q
What happens to offspring of sexual species in regards of genetics?
A
Each offspring is genetically different from its parents
This genetic variation is crucial for the adaptability of species.
10
Q
What can varying susceptibility to diseases help individuals within a family do?
A
Survive a new plague
Some individuals may possess traits that confer resistance to evolving diseases.
11
Q
Fill in the blank: Resistance to evolving infectious diseases is a benefit of _______.
A
sex
Sexual reproduction leads to genetic diversity, which can enhance disease resistance.
12
Q
True or False: All Cavendish banana plants can produce seeds.
A
False
Cavendish plants are sterile and do not produce seeds.
13
Q
Is sex good for anything that happens in a shorter time scale than speciation?
A
Yes, it contributes to resistance to evolving infectious diseases.
This suggests that sexual reproduction may enhance a population’s ability to adapt to rapidly changing environmental challenges, such as disease pressures.
14
Q
What is the developmental biology of sex?
A
It refers to how males and females are made during development (In some species true hermaphrodites exist - generate both male and female gametes.)
15
Q
What are true hermaphrodites?
A
Species that generate both male and female gametes.
16
Q
What are the two distinct phases of sex development?
A
- Sex determination
- Sexual differentiation
17
Q
What is sex determination?
A
The decision to execute male or female patterns of development.
18
Q
What is sexual differentiation?
A
The execution of the decision to create a male or a female developmental state.
19
Q
Write a list of examples of sex determination system
A
20
Q
Explain the xy system
A
21
Q
What chromosome combination indicates a female in mammals?
A
XX
22
Q
What chromosome combination indicates a male in mammals?
A
XY
23
Q
Do males have all the genes that females have?
A
Yes
24
Q
How many copies of the X chromosome do males have?
A
1
25
How many copies of the X chromosome do females have?
2
26
What chromosome do males have that females do not?
Y
27
What is the mammalian XY sex determination system?
A genetic process that determines sex in mammals
## Footnote
This system is crucial for understanding sexual differentiation.
28
How many X chromosomes are sufficient for female gonad and genital development?
One X chromosome
## Footnote
This indicates that the presence of a single X is enough to initiate female development.
29
What is sufficient to drive male gonad and genital development?
One Y chromosome
## Footnote
The presence of a Y chromosome is key for male development.
30
True or False: An XX individual can develop male gonads if they have a Y chromosome.
True
## Footnote
This is illustrated by the XXY condition, where the Y chromosome can override the XX configuration.
31
Fill in the blank: One Y is sufficient to drive _______ gonad and genital development.
male
## Footnote
This highlights the role of the Y chromosome in male differentiation.
32
What happens in an XXY individual regarding sex determination?
The presence of the Y chromosome drives male development
## Footnote
This can result in conditions such as Klinefelter syndrome.
33
What does 'chromosomal' refer to in genetics?
'Chromosomal' defines mutations that cause significant alteration to chromosomes, including deletions, insertions, and translocations of sections of a chromosome.
34
What are point mutations?
Point mutations are mutations that affect only one gene.
35
Fill in the blank: 'Chromosomal' mutations include _______.
deletions, insertions, translocations
36
True or False: Chromosomal mutations affect only one gene.
False
37
List three types of chromosomal mutations.
* Deletions
* Insertions
* Translocations
38
What does SRY stand for?
Sex Determining Region of Y
## Footnote
The SRY gene is crucial for male sex determination.
39
What is another term used to refer to the SRY gene?
TDF - testis-determining factor
## Footnote
TDF is an older term that emphasizes the gene's role in testis formation.
40
What is the role of the SRY gene?
The SRY gene causes maleness.
41
What is the outcome of an XX mouse with an SRY transgene?
The XX mouse with an SRY transgene is male.
42
What does the presence of the SRY gene indicate?
The presence of the SRY gene indicates maleness.
43
What is the outcome in the absence of the SRY gene?
The absence of the SRY gene results in female.
44
What does the SRY gene encode?
A protein that is a transcription factor
## Footnote
The SRY gene is crucial for male sex determination.
45
What does SRY bind to?
[T/A]AACAA[T/A]
## Footnote
This binding is essential for regulating the expression of other genes.
46
How many genes determine making 'a gonad'?
Two
## Footnote
These genes are critical in the process of gonadal development.
47
How many genes determine sex - male or female gonad?
Three
## Footnote
These genes play a role in establishing the sexual phenotype.
48
Which gene is found only on the Y chromosome?
SRY
## Footnote
The presence of SRY is essential for male development.
49
What do the three sex determining genes constitute?
A molecular switch
## Footnote
This switch is crucial for determining the sex of the organism.
50
Explain SRY and the mammalian sex determination switch
Sex Undetermined Stage: The embryo starts as an "indifferent" early embryo, meaning it has not yet developed male or female characteristics.
No SRY gene present → The embryo is in a Pre-Female state (highlighted in yellow).
SRY gene present → The embryo is in a Pre-Male state (highlighted in blue).
Genes like SF1 and WT1 are “ make a gonad gene” expressed in both XX and XY embryos in the “Indifferent Gonad” tissue (green box).
Determination (~6-week human embryo):
If WNT4 is ON → The embryo moves towards female development.
If SRY is present, it activates SOX9, which in turn turns OFF WNT4, pushing the embryo toward male development.
Sex Differentiation (Gonad Development):
If WNT4 remains ON → The gonad develops into Ovary & Female (yellow). This leads to the production of estradiol, a key female hormone.
If SRY is ON → SOX9 is activated → WNT4 is turned OFF → The gonad develops into Testes & Male (blue). This leads to the production of testosterone, a key male hormone.
51
What is the initial state of the embryo regarding sex determination?
The embryo starts as an 'indifferent' early embryo
52
What does the absence of the SRY gene indicate about the embryo's state?
The embryo is in a Pre-Female state
53
What does the presence of the SRY gene indicate about the embryo's state?
The embryo is in a Pre-Male state
54
Which genes are expressed in both XX and XY embryos in the 'Indifferent Gonad' tissue?
SF1 and WT1
55
What happens if WNT4 is ON during the determination stage?
The embryo moves towards female development
56
What role does the SRY gene play in male development?
It activates SOX9, which turns OFF WNT4
57
What is the result if WNT4 remains ON?
The gonad develops into Ovary & Female
58
What hormone is produced when the gonad develops into an Ovary?
Estradiol
59
What is the result if SRY is ON?
The gonad develops into Testes & Male
60
What hormone is produced when the gonad develops into Testes?
Testosterone
61
Fill in the blank: If the SRY gene is present, it activates ______, which turns OFF WNT4.
SOX9
62
True or False: WNT4 is a gene that promotes male development.
False
63
What is the consequence of SOX9 activation in the context of sex differentiation?
It leads to the gonad developing into Testes & Male
64
What protein is present in males that leads to the differentiation of somatic gonadal precursor cells into Sertoli cells?
SOX9
## Footnote
SOX9 is crucial for male sex determination.
65
What hormone do Sertoli cells secrete in males?
Anti-Mullerian Hormone (AMH)
## Footnote
AMH plays a key role in male reproductive development.
66
What do somatic gonadal precursor cells differentiate into after being promoted by AMH?
Leydig cells
## Footnote
Leydig cells are essential for testosterone production.
67
What steroid hormone do Leydig cells produce?
TESTOSTERONE
## Footnote
Testosterone is vital for male phenotype development.
68
What drives all other male phenotypes, including genitals and behavior?
Testosterone
## Footnote
Testosterone influences male fertility as well.
69
In females, what is absent that leads to the differentiation of somatic gonadal precursor cells into Theca and Granulosa cells?
No SRY
## Footnote
The absence of SRY is critical for female development.
70
What are the steroid hormones produced by Theca and Granulosa cells in females?
ESTRADIOL and PROGESTERONE
## Footnote
These hormones are important for female reproductive functions.
71
What drives all other female phenotypes, including genitals and behavior?
Lack of Testosterone and presence of estradiol & progesterone
## Footnote
Female reproductive health is influenced by these factors.
72
What do sex-specific gonads produce in mammals?
Sex-specific patterns of SEX STEROID HORMONES
73
What is the primary sex steroid hormone produced in males?
Testosterone
74
What are the primary sex steroid hormones produced in females?
Estradiol and Progesterone
75
What do sex steroids regulate in mammals?
All sex-specific differences
76
What are other anatomical reproductive differences influenced by sex steroids?
Uterus, urinary systems etc.
77
What are some anatomical and physiological differences influenced by sex steroids?
Bone density, muscle size, body size etc.
78
In some species, what patterns of adult hair growth are influenced by sex steroids?
Facial hair and male pattern balding in humans
79
What types of behavior are influenced by sex steroid hormones?
Mate selection, offspring rearing, territorial aggression etc.
80
The sex steroids regulate all sex-specific differences in mammals, list these differences
The sex steroids then regulate all other sex-specific differences in mammals.
• Male or female patterns of GENITAL development in the embryo.
• Other anatomical reproductive differences (uterus, urinary systems etc.)
• All other anatomical and physiological differences - bone density, muscle size, body size etc.
• In some species patterns of adult hair growth (facial hair and male pattern balding in humans)
• Patterns of behaviour – mate selection, offspring rearing, territorial aggression etc.
81
What are steroids made from?
Cholesterol
82
What is the role of a cognate receptor in relation to steroids?
It is a protein receptor that binds to testosterone
83
What is required for male pattern development besides testosterone?
A functional receptor for testosterone
84
What happens without a functional androgen receptor (AR)?
Testosterone cannot trigger the genetic changes required for male differentiation
85
Fill in the blank: Steroids have a cognate receptor, a protein receptor that binds to _______.
testosterone
86
What is the function of Aldosterone?
Salt/water balance
87
What role does Corticosterone play in the body?
Inflammation
88
What does DSD stand for?
Disorders of Sexual Development
89
What is an example of a steroid hormone receptor involved in DSDs?
Androgen receptor
90
List some sex determination genes that can cause DSDs when mutated.
* SRY
* SOX9
* SF1
* WT1
* WNT4
91
What can mutations in sex determination genes lead to in terms of gonadal defects?
DSDs with various gonadal defects and sex reversals
92
True or False: DSDs only result in physical abnormalities.
False
93
What is a common outcome of DSDs related to reproduction?
Reproductive difficulties/sterility
94
Fill in the blank: DSDs can be caused by mutations in _______.
SRY, SOX9, SF1, WT1, WNT4
95
What is the relationship between steroid hormone receptors and DSDs?
Steroid hormone receptors are involved in the hormonal regulation that can affect DSDs
96
What is the initial state of gonad development before sex determination?
Anatomically and physiologically identical in both future sexes
## Footnote
This state is referred to as the Indifferent Gonad.
97
What happens to indifferent gonads after successful sex determination?
They will develop into testes or ovaries.
98
What do Genital Ridges contain?
Somatic Gonadal Precursor Cells
## Footnote
Genital Ridges are essential in the development of the gonads.
99
Where do Germline stem cells migrate from?
Hindgut
## Footnote
This migration is crucial for the formation of gonads.
100
What do the Genital Ridges become?
Indifferent Gonads
## Footnote
Indifferent Gonads contain both somatic gonadal cells and germline stem cells.
101
What type of cells do Indifferent Gonads contain?
* Somatic gonadal cells
* Germline stem cells
## Footnote
These cells are key for further development into functional gonads.
102
What type of kidney persists as the adult kidney?
Metanephric kidney
103
What is the embryonic kidney called?
Mesonephros
104
True or False: The mesonephros is distinct from the adult kidney.
True
105
What structure is a single posterior opening that divides to create anal and urethral openings?
Cloaca
106
What does the Wolffian Duct become in males?
The vas deferens
## Footnote
The Wolffian Duct is crucial in male reproductive development.
107
What does the Mullerian Duct become in females?
The oviduct
## Footnote
The Mullerian Duct is essential for female reproductive system development.
108
What is the first stage of genital development called?
Indifferent Stage of Genitals
109
In males, what do the genital swellings fuse to form?
Scrotum and penis
110
What do the genital folds in males create?
A tube that extends the urethra
111
In females, how do the genital swellings develop?
They stay separate to form labia majus
112
What do the genital folds in females develop into?
Labium minus
113
What is formed from the glans component in females?
Clitoris
