03 - Behavioral Sex Flashcards
(Behavioral Sex)
Males and females show many sexually dimorphic behaviors that either occur or are imprinted prior to the large differences in sex-specific steroid secretion that occur during and following puberty.
(examples)
- urination posture in dogs and sheep (humans? anatomic vs learned vs imprinted)
- rough and tumble play in most species is more evident in juvenile males or females?
- males
(Behavioral Sex)
- These behaviors are largely thought to be set during sexual differentation of the brain in what stage?
READ THIS
Other behaviors, while set early in life, may not be evident until after the occurrence of puberty and its high circulating steroid levels. In studied species, mate preference appears to be developmentally programmed to some extent by exposure to androgen in the perinatal sensitive period but is not activated until re-exposure to androgens at puberty (males).
Still other behaviors observed post-puberty require no apparent organizational changes – they can be induced in animals exposed to steroids for the first time as adults.
Trying to find which brain dimorphism results in which behavior can be difficult and the work that has been done is largely confined to laboratory animals and some birds.
- e.g. copulatory behavior - SDN of POA rats, voles male > female
Another problem is that behavior can vary depending on how it is observed:
“Crying infant response” in male and female rhesus monkeys
When tested separately both male and female monkeys respond
When tested together only female responds
- late fetal or neonatal period (thus in female rats behavior can be masculininzed by a single adrogen injection in the first few days of life)
(Legal Sex)
- occasionally the law is asked to determine the sex of an individual
just read…
(M. Sex Determination in Birds)
Like mammals, birds use a genetic method of sex determination… we don’t know how it works
- what sex is ZW?
- what is ZZ?
- Is there homology between the Z and W chromosomes of birds (+ reptiles) and the X and Y chromosomes of mammals?
- Has an Sry equivalent been identified in birds?
1-4. What are the four possibilities of how this works?
- female (hetero sex)
- male (homologous)
- no
- no
(if there was it would most likely be on female W)
- dosage system (males have two Z to females 1)
- dominant W (something on W determines)
- Cell autonomous Sex Identitiy (CASI - combo of above two)
- some combo of above
(M. Sex Determination in Birds)
- Are steroids used for correct gonadal development in birds?
- what combo for males?
- for females?
- yes
- avoid estrogen, adequate levels of testosterone and MIS
- estrogens act as fundamental signal (for ovarian development)
(Sex Determination in Birds)
(Sex chromosome Dosage Model)
- strongest evidence is for birds using what system? What is this supported by?
- Birds also start development with an indifferent gonad, the cortex giving rise to the ovary and the medulla to testes
- dosage (having two Z sends towards male); birds don’t have dosage compensation mechanism (males have twice the activity of Z linked genes (DMRT1)
(Sex Determination in BIrds)
(development of the male)
- bilateral testes develop under what hormonal conditions?
- What is the canidate Z chormosome for sex differentiation?
how does this work?
- Does DMRT1 directly cause differentiation of Sertoli cells?
acts by doing what?
- What is the other function of DMRT1 in regard to females?
- lack of estrogen, presence of testosterone/MIS
- doublesex and Mab-3-related transcription factor (DMRT1)
twice of this sends down male, one allows ovarian genetic cascade
- no (earliest cell to differentiatite during testicular development)
increasing sox9 (unkown if direct or if interemediates involved)
- down-regulate female pathway (by suppressing FOXL2)
(Sex Determination in BIrds)
(development of the female)
- in the presence f one DMRT1 female pathway not inhibited
- Ovarian formation requireds induction of what enzyme? and thus what?
- Resulting estrogen causes what?
(other genes in female determination pathway a similar to mammals (WNT4, RSP01) - an example of how conserved these mechanisms are)
- aromatase enzyme; estrogen production (this appears to be function of FOXL2)
- causes bipotential gonad to differentiate as an ovay and prevents testicular development
(FOXL2 also prevents transcription of DMRT1 - further reducing formation of testes)
(Sex Determination in BIrds)
(development of the female - cont)
- In females of most bird species does only the right or left ovary develop?
- why?
- exceptions with bilateral ovaries?
- left (right regresses) (local action of extrogen from ovary preserves and develops the left oviduct)
- estrogen receptors down-regulated on right gonad of females in these species (on both in genetic males)
- Falconiformes and kiwi
(SEx Determination in Birds)
( A role for the W)
- While no dominant sex determing gene appears to exists… there is some evidence of genes on what chromsome involved in ovarian formation?
- ZZW start life appearing female… but soon change appearance to male - what does internal look like?
- W chromosome
- right testis, left ovitestis (however some ZZW birds of other species are fertile females)
(Sex Determination in BIrds)
(3. CASI)
1. with presence of occasional gynandromorps (laterally half male half female) - birds are poster children for CASI - what does this stand for?
2. sex phenotype of each cell in the body not determined by hormone exposure… but by what?
3. This applies particularly to cells outside the reproductive tract but in affected chickens the phenotype of the left gonad followed the genetic makeup of the cells, indicating a CASI role here too. However the genetic identity of the gonadal cell can be overcome by manipulating individual genes or hormones (e.g. estrogen) involved in gonad development, so CASI isn’t the whole story.
- cell autonomous sex identity
- genetic makeup of cell itself
the next few pages are all small type… so probably don’t need to know but look into it
