Deck 9: Sexual Behavior

Question 1

Male-specific development and behavior is mediated by:
(a) testosterone.
(b) dihydrotestosterone.
(c) estradiol.
(d) a and b
(e) All of the above

Answer 1

(E)
Although testosterone and its metabolite dihydrotestosterone are considered to be the androgenic hormones, testosterone converted to estradiol by aromatase acts through estrogen receptors.

Question 2

In both insects and mammals:
(a) sexual dimorphism in the brain is often due to sex-specific differences in programmed cell death.
(b) sexual dimorphism is regulated by reception of circulating sex hormones.
(c) sex determination is cell-autonomous, based on karyotype.
(d) sex-specific survival of a muscle promotes survival of its motor neuron(s).
(e) All of the above

Answer 2

(A)
In mammals, sexual determination is regulated by reception of circulating sex hormones, while in insects, it is cell-autonomous, based on sex chromosome complement. Also, while in mammals the sex-specific survival of a penile muscle promotes survival of its motor neurons, the opposite is true in flies, in which survival of a Fru^M motor neuron is necessary and sufficient for the survival of the muscle of Lawrence.

Question 3

Some aspects of bird song are innate, while others must be learned and practiced. What kind of song would be produced by a male bird with a lesion in area X who was raised with a tutor male of a different species?
(a) No song at all
(b) A species-specific rudimentary innate song similar to that of acoustically isolated birds
(c) A rudimentary innate song distinct from that of acoustically isolated birds
(d) A mature song that resembles that of his own species
(e) A mature song that resembles that of the tutor's species

Answer 3

(C)
Isolated birds still produce a species-specific rudimentary song, but even this 'innate' song requires trial-and-error learning during the sensorimotor stage since deafened birds produce an altered song. A bird with a lesion in area X should also be incapable of this trial-and-error learning, regardless of the species of the tutor.

Question 4

Unisexual whiptail lizards exhibit male-like courtship behavior when:
(a) their ovaries are enlarged.
(b) their endogenous estrogen levels are high.
(c) their endogenous testosterone levels are high.
(d) their endogenous progesterone levels are high.
(e) All of the above

Question 5

In mammals, the TrpC2 channel is essential for all of the following except for:
(a) olfactory transduction in the accessory olfactory system.
(b) males to exhibit normal mating behavior towards females.
(c) males to exhibit aggression towards intruder males.
(d) males to distinguish between different strains of mice.
(e) females to exhibit female-typical behaviors.

Question 6

Drosophila females' receptivity to courtship is inhibited by:
(a) activity in the neurons equivalent to those that express Fru^M in males.
(b) sex peptide transferred in seminal fluid during copulation.
(c) activity in sensory neurons in the uterus.
(d) All of the above
(e) None of the above

Question 7

Would you expect to see male-typical behavior in adult rodents that have undergone each of the following treatments (Y/N)? Briefly explain your reasoning in each case.
A. Are XY but have the aromatase gene knocked out in the brain
B. Are XY but have the androgen receptor knocked out in the brain
C. Are XX but were treated with exogenous estradiol during the first ten days after birth
D. Are XX but were exposed to exogenous testosterone prenatally and then again as adults
E. Are XX but were treated with exogenous dihydrotestosterone during the first ten days after birth

Question 8

During the breeding season, the vocal control areas are significantly larger in male canaries than in females of the same species due to:
(a) sex hormones.
(b) brain-derived neurotrophic factor.
(c) adult neurogenesis.
(d) recruitment of new neurons into functional circuits.
(e) All of the above

Question 9

The inhibition of infanticidal behavior requires:
(a) the vomeronasal organ in males.
(b) the TrpC2 channel in males.
(c) galanin-expressing neurons of the medial preoptic area in parents.
(d) galanin-expressing neurons of the medial preoptic area in virgin females.
(e) All of the above

Question 10

The Drosophila courtship ritual is considered to be an innate behavior-why? Does this mean that this behavior is not influenced by experience? Briefly explain your reasoning.

Question 11

For chromosomally female (XX) flies that carry a Fru^Δ mutation, all of the following are true except:
(a) they have the physical appearance of males.
(b) they tap female flies with their forelegs.
(c) they sing by vibrating one of their wings.
(d) they lick the genitalia of female flies.
(e) they attempt (but do not complete) copulation.

Question 12

Activation of the following neurons in a wild-type XY fly should promote courtship:
(a) olfactory receptor neurons that innervate the DA1 glomerulus.
(b) projection neurons that innervate the DA1 glomerulus.
(c) DC1 neurons in the lateral horn of the protocerebrum.
(d) projection neurons that innervate the VL2a glomerulus.
(e) All of the above

Question 13

Conditional silencing allows researchers to test whether particular sets of neurons are required for specific behaviors. You suspect that a set of neurons expressing a gene called drifter might be involved in Drosophila courtship. Describe the tools that you would need and the experiments (and controls) that you would use to test your hypothesis.

Question 14

All of the following karyotypes result in male development except:
(a) XO in flies.
(b) XY in flies.
(c) XO in humans.
(d) XXY in humans.
(e) XY in humans.

Question 15

Just as sexual behavioral circuits in flies were dissected using a GAL4 driver that had been knocked into the Fru locus, genetic manipulation of subsets of neurons expressing sex hormone receptors can provide insights into the function of specific brain nuclei in mammalian sexual behavior.
A. How could the Cre/loxP system be used to determine whether estradiol receptor-expressing neurons in the VMH are necessary in males for mating with females and aggression towards intruder males?
B. What experimental evidence suggests that estradiol reception by VMH neurons is sufficient to produce either mating or aggression, depending on the intensity of the stimulus?
C. Suggest some experiments that could be used to help determine whether the same population of VMH neurons mediates mating vs. aggression in males.

Question 16

The medial preoptic area, medial amygdala, and bed nucleus of stria terminalis are larger in male rodents than in their female counterparts. Postnatal castration reduces the size of these nuclei in males, while neonatal testosterone treatment or inhibition of programmed cell death increases their size in females. Are these sexual dimorphisms due to direct action by testosterone or by estradiol? Describe at least two experiments and outcomes that would allow you to distinguish between these models.

Question 17

XY fruit flies that are mutant for Tra:
(a) have the physical appearance of females.
(b) express Dsx^F.
(c) make a long mature version of the Fru mRNA.
(d) make a full-length version of the Fru protein.
(e) All of the above

Question 18

Which of the following conditions would be expected to correlate with an increase in circulating testosterone from exogenous androgenic steroid use (for example, by athletes)?
(a) An increase in LH/FSH release by the anterior pituitary
(b) An increase in GnRH release by the hypothalamus
(c) An increase in Kiss1 release by the arcuate nucleus
(d) An increase in secondary sex characteristics such as muscle mass, body hair, and aggression
(e) An increase in testis size

Question 19

Sex-specific splicing of both Fruitless and Doublesex is essential for the establishment of normal neuronal circuitry underlying courtship behavior. Please indicate whether Dsx^F or Fru^M is responsible for each of the following functions.
A. Promotes programmed cell death in developing P1 neurons
B. Prevents programmed cell death in the motor neuron innervating the muscle of Lawrence
C. Promotes male-typical projection patterns in developing P1 neurons
D. Prevents midline crossing by taste receptor neurons on the foreleg
E. Promotes projection patterns in third order neurons that mediate aggression in response to the male pheromone cVA

Question 20

Infusion of oxytocin into the brain of an ovariectomized (unreceptive) female prairie vole is sufficient for her to develop preference for a nearby male. But what is the neurological basis for this preference? There are established techniques for making knockout and transgenic mice, but since mice do not exhibit pair-bonding behavior, researchers are currently developing similar techniques for use in voles. Describe some specific experiments that you would like to perform in order to determine in which neurons oxytocin reception is present, necessary, and sufficient for female vole partner preference.

Question 21

Which neuropeptide is associated with each of the following processes? Select oxytocin, vasopressin, both, or neither.
A. Acts through a G-protein-coupled receptor in peripheral tissues
B. Regulates blood pressure homeostasis in both sexes
C. Promotes milk production in females
D. Promotes partner preference in male meadow voles
E. Promotes partner preference in male prairie voles
F. Is released from the posterior pituitary into the bloodstream

Question 22

Nematocin appears to be a homolog of vasopressin/oxytocin because:
(a) its receptors are most closely related to mammalian vasopressin and oxytocin receptors.
(b) its precursor protein shares conserved structures with those of vasopressin and oxytocin.
(c) its mature form shares structural features with vasopressin and oxytocin, particularly the disulfide bond between the first and sixth amino acids.
(d) it is necessary for normal reproductive behaviors.
(e) All of the above