HW - Sexual Dimorphism II Flashcards
What are some characteristics of birdsong? (5)
Bird song:
- Long and complex
- Made up of syllables
- Expiration
- Tympanic membrane vibration
- Pitch and volume modulation
What are the stages of song development shown in the timeline? (3)
- Sensory (memorize tutor song),
- Sensorimotor (immature song/compare)
- Crystallized (mature song)
What are some features related with sexual dimorphism in the whiptail lizard (all ♀)? (7)
- Parthenogenesis (development from unfertilized eggs)
- Pre-meiotic endoreplication (2n oocytes)
- Courtship behaviour stimulates ovulation
- Progesterone associates with ♂-like behaviour
- Progesterone acts in MPOA-equivalent area of hypothalamus
- Oestrogen associates with ♀-like behaviour
- Oestrogen acts in VMH-equivalent area of hypothalamus
What gene is found on the human Y chromosome?
SRY gene: The Y chromosome contains a gene called SRY (Sex-determining Region on the Y) gene
- This gene is responsible for triggering the development of testes in males
What are some common genetic disorders which result in intersexuality in humans? (6)
1) Klinefelter syndrome (XXY): This disorder occurs when a person has an extra X chromosome. People with Klinefelter syndrome are born with testes but may have underdeveloped testes and male genitalia. They may also develop breast tissue.
2) Turner syndrome (XO): This disorder occurs when a person is missing one X chromosome. People with Turner syndrome may be born with underdeveloped ovaries and female genitalia. They may also have short stature and other health problems.
3) 47-XYY syndrome: This disorder occurs when a person has an extra Y chromosome. People with 47-XYY syndrome are typically born with male genitalia and appear male. However, they may have a higher risk of learning disabilities and behavioral problems.
4) Congenital adrenal hyperplasia (CAH): This is a group of disorders that affect the adrenal glands. In some cases, CAH can cause the overproduction of androgens in females, which can lead to virilization of the external genitalia.
5) Androgen insensitivity syndrome (AIS): This disorder is caused by a mutation in the androgen receptor gene. People with AIS are genetically male (XY), but their bodies are not able to respond to testosterone. This can result in the development of female external genitalia and breast tissue.
6) Testes-determining factor mutation: Mutations in the SRY gene can interfere with testis development. This can result in people with XY chromosomes being born with female external genitalia.
Describe the sex hormones’ mode of actions
Male:
- Testosterone diffuses
across the plasma membrane, binds to the androgen receptor, and causes nuclear translocation of the complex. The complex binds to promoters of target genes to regulate their transcription
Female:
- Estradiol diffuses across the plasma membrane, binds to the estrogen receptor, and causes nuclear translocation of the complex. The complex binds to promoters of target genes to regulate their transcription
The androgen and estrogen receptors both act as homodimers
Where does intracellular estradiol derive from?
Circulating estradiol or from circulating testosterone converted to estradiol by the enzyme aromatase
What are the direct and indirect actions of steroids on the brain?
Direct
Alters neurotransmitter
- Synthesis
- Release
- Reuptake
Indirect
- Promotes or inhibits transcription
What are the 3 major receptros/transcription factors that bind estrogen and androgen in the rat brain?
Bind estrogen (ERα and ERβ)
Bind androgen/testosterone (AR)
What acts to block maternal estrogen in ♀,♂
fetal brain in rodent utero?
a-Fetoprotein
Organizational vs Activational effects (in rodent brain)
- Organizational effects happen during a critical period early in development (E18 to P10) and set up the basic structure of the brain.
- Activational effects occur later, around puberty (P40) and influence sex-specific behaviors.
How does steroid action determine sex in rodents? (5)
In Females:
- No testosterone is produced
- Estradiol does not circulate the brain
- Little ER activation
- Altered gene expression
- Feminised brain
Male:
- Testosterone crosses the mebrane
- Testosterone –> Estrogen (Aromatase)
- ER activation
- Altered gene expression
- Defeminised brain
What acts to stimulate GnRH release from GnRH neurons?
Kisspeptins released from Kiss1 neurons in the arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV)
What is the significance of GnRH neurons?
Puberty is marked by activation of gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus
What is the function of GnRH?
GnRH circulates to the anterior pituitary, where it stimulates endocrine cells to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
- The bloodstream transports LH and FSH to the gonads (testes or ovaries), which respond by producing steroid sex hormones that regulate the differentiation of secondary sex characteristics during puberty.
