LM2 Flashcards
Describe how to determine the sex of a box turtle
- Male: Back toes are thicker and highly curved
* Female: Back toes are thinner and straighter
Describe the genetic sex of mammals
- XX, XY
- Sex ratio of 1:1
- Males: heterogametic sex
- Females: Homogametic sex
Describe the genetic sex of avians
- ZZ, ZW
- Female: heterogametic sex
- Male: Homogametic sex
How is sex determined in crocodilians and turtles?
Temperature
Describe the effect of temperature on sex in american alligators
- Deviated sex ratio of 8M:1F
- High temps=males
- Low temps=females
Describe the effects on sex by temperature of painted turtles
- Incubation temp of 25C= 79%M and 21% Unknown
* Incubation temp of 30.5C= 80%F and 20% Unknown
What incubation temps result in predominantly female snapping turtles?
- 20C
- 22C
- 30C
What incubation temps result in predominantly male snapping turtles?
- 24C
- 26C
- 28C
What are the 5 modes of reproduction
- Sexual Reproduction
- Parthenogenesis
- Gynogenesis
- Hybridogenesis
- Interconversion of Sexual Types
- Hermaphrodism
Describe sexual reproduction
- 2 haploid (C) gametes (X and Y)
* Gametes fuse creating a new diploid individual
What are the advantages of sexual reproduction
- Genetic recombination
* Hybrid vigor resulting in increased fitness
What animals participate in Pathenogenesis
- Bonnethead Shark
* Marbled crayfish
Describe Parthenogenesis
- Non-sexual reproduction: fully inbred line
- Oocyte at metaphase 2 undergoes self-activation
- Karyokinesis without cytokinesis
- OR can undergo non-disjunction at metaphase 2 (ctyochalasin B)
What are the advantages of Parthenogenesis
All members of the population reproduce (female)
What are the disadvantages of Parthenogenesis
- Less hybrid vigor
* More sensitive to environmental changes
What species utilize Gynogenesis
Some Poecilia (guppy) species
Describe gynogenesis
- Sex method: XX=Female, highly inbred line
- A.K.A sperm activated parthenogenesis
- Sperm DNA doesn’t participate-binds egg but doesn’t enter
- Live bearers w/internal fertilization
What are the advantages of gynogenesis
- Population expands rapidly (all are able to reproduce)
* Males: some other species can activate the females
What species participate in hybridogenesis
Some Poecilia (guppy) species
Describe hybridogenesis
- Sexual reproduction producing only females
- Live bearers
- Sex method: ZW=Female, ZZ=male (other species)
- Eggs are always the W gamete, sperm DNA to polar body
What are the advantages of hybridogenesis
- All female population so all can reproduce
- Sexual reproduction increases hybrid vigor in zygote
- Subordinate males of other species can get breeding practice
What species participate in Interconversion of sexual types
Bluehead wrasse (coral reef fish)
Describe the breeding group of interconversion of sexual types
- Dominant male: large and highly colored so suspect to predation
- Size heirarchy dominance w/in females of the group
Describe what occurs upon loss of the dominant male in interconversion of sexual types
- Largest female becomes next male
- 0hr- male removed
- +2hr-largest female exhibits aggressive behavior
- +2-4d-largest female exhibits male sexual behavior
- +14-18d-largest female now a true breeding male
What species utilizes hermaphrodism
Angler fish is an ‘acquired’ true hermaphrodite
Describe hermaphrodism of the angler fish
- Sexual reproduction from one individual
- 2 sets of reproductive organs
- 2 separate orifices
- external fertilization
- Up to 6 males can be absorbed into the female’s body and is referred to as a multiple hermaphrodite
What is XXX referred to as and how does this affect fertility
- Superfemale
* fertile
What is XO referred to as and how does this affect fertility
- Turner’s syndrome
* Sterile
What is XXY referred to as and how does this affect fertility
- Klinfelter’s syndrome
* Sterile
What is XYY referred to as and how does this affect fertility
- Supermale
* fertile
What is XX with testis referred to as and how does this affect fertility and how does it occur
- Sex reversed male
- Fertile
- An X chromosome carries a small piece of the Y chromosome via non-disjunction
Where are Barr bodies present?
All somatic cells
How many barr bodies does an XX female have
1
How many barr bodies does an XXX female have
2
How many barr bodies does an XY male have
none
How many barr bodies does an XXY male have
1
When did Sry History begin?
Karyotyping in 1959
What happened in 1966 in relation to discovering Sry?
Sex-reversed identified in mice
What happened in 1986 in relation to discovering Sry?
- Molecular biology techniques (cut part of the Y chromosome with restriction enzymes)
- YP1 identified as the 1st portion of the chromosome underneath the pseudoautosomal pairing region (pairs with X chromosome in meiosis)
- Determined YP1 was always present in phenotypically male individuals
What happened in 1987 in relation to discovering Sry?
- A gene of the YP1 was isolated and designated as Zfy
* Zfy s a transcrition factor with a zinc-finger region
What happened in 1989 in relation to discovering Sry?
- Sry identified and noted as present in all sex-reversed individuals
- Determined Sry was the sex determining region on the Y chromosome
- It was determined that Sry is 250bp long, has no introns, and codes a protein that is only 80aa long
- It was also determined that Sry is a transcription factor
What happened in 1990 in relation to discovering Sry?
*Sry determined to be the testis-determining factor in mammals
What happened in 1991 in relation to discovering Sry?
- Generation of transgenic XX-Sry male mice
- Mouse zygotes were injected with the Sry gene adn transferred to a recipient
- Male pups were analyzed via karyotyping and PCR and they found XXSry males that were fertile
Describe the 3 general factors of Sry mechanism of action
- Acts as a transcription factor
- Induces sertoli cell differentiation
- Leads to testis formation
Describe the general Sry mechanism of action in males
- Sry activates Sox9
- This causes sertoli cell differentiation
- This also causes Fgf9 to block Rspo1/Wnt4 which blocks female pathway
Describe the general Sry mechanism of in females
- Respondin 1 blocks Sox9 to block sertoli cell differentiation
- High Rspo1 and Wnt4 cause pre-granulosa cell differentiation
When does Sry expression peak in gestation in mice
day 11.5
Describe how Sry activates Sox 9 and the effects of its activation
- Sry is moved to the nucleus via Ca-Calmodulin and Impß
- Sry binds to DNA to turn on Sox9 expression
- Sox 9 continues to induce its own expression resulting in sertoli cell differenctiation
- This leads to AMH production and T production
- Sox9 continues the actions of Sry to promote complete testicular development
Describe primordial germ cell origin and migration
- PCGs originate from yolk sac endoderm
- They migrate to genital ridges in developing embryo
- They will become either spermatogonia or oogonia dependent upon sex determination factors
Describe incorrect PCG Migration
- Degeneration occurs if PCGs are not associated with the support cells
- Males need sertoli cells
- Females need pre-granulosa cells
Describe the reproductive tract development of Mammals
- Male: Wolffian Ducts androgen dependent and MIH (or AMH) is required to regress the Mullerian Ducts
- Female: Mullerian ducts (no androgens or MIH)
Describe reproductive tract development in aves
- Wolffian ducts in both males and females and are not androgen dependent
- Female left ovary and left Mullerian duct only because E2 causes the right MD to regress
Describe reproductive tract development in reptiles and fish
- Wolffian ducts in both males and females and is not androgen dependent
- Males: Mullerian ducts regress due to androgens
- Females: Plasticity of tract potential, once become male can’t revert back to female however
What is the intrauterine position phenomenon
Refers to intrauterine position relative to sex of siblings and its affects (found in mice)
What type of IUP has the following effects:
- Elevated E2 production
- Short anogential distance at birth
- Attracted to males
- Strong behavior response (lordosis)
- Low female aggression
- 4 day estrous cycle
- early onset puberty
0M Female
What type of IUP has the following effects:
- Elevated T production
- Longer anogential distance at birth
- Less attracted to males
- Low lordosis
- High female aggression
- 5-6 day estrous cycle
- Late puberty
2M female
What are the effects of IUP on the first litter of both 0M females and 2M females
- 0M female: 42% males
* 2M female: 59% males
What are the effects of IUP on the second litter of both 0M and 2M females?
- 0M female: 45% males
* 2M female: 53% males
Describe the methods of the maternal stress exeperiment
- Pregnant female mice underwent stress or control dyas 12-17 of gestation
- Stress was to have lights turned on, removal from cage, held in small restraining chamber for 45min twice daily
- AGI was measured in female offspring at C-section
- Estrous cycle of 0M vs 2M offspring was measured after they reached puberty
What were the results of the maternal stress experiment and what are the implications of this
- 0M had significantly longer AGI and longer estrous cycle
- Maternal stress masculinizes 0M female offspring
- Differentiation and reproductive characteristics can be modified by the intrauterine environment
