Lecture 3

Question 0

What eliminates male sex behavior and what restores it.

Answer 0

Castration eliminates male behavior and testosterone replaces it.

Question 1

Describe differences between male and female rodents in reference to mating behaviors.

Answer 1

Females express lordosis and males mount to females. They both rarely do the opposite.

Question 2

Does testosterone cause mounting behavior?

Answer 2

No. It acts as a critical period of development to program sexual behavior.

Question 3

Describe Young’s hypothesis and his results.

Answer 3

Gonadal steroid hormones must act early in development to induce sexually dimorphic mating behavior. Results showed despite being given Steroid hormones in adulthood that typically induce sex behaviors, all adults guinea pigs exposed to testosterone early in life displayed impaired lordosis and enhanced mounting.

Question 4

What are the four conclusions of the organizational/ activation hypothesis

Answer 4

1. Prenatal steroid hormones = organization of sex differences
   Postnatal/ adult steroids = activation of differentiated system
2. Critical periods exist for steroid hormones
3. Organization is masculine/ feminine
4. Organization can have subtle effects

Question 5

Why are there sex differences? And how do they develop.

Answer 5

The causes are evolution and adaptation. They develop through mechanisms.

Question 6

What are the three observations of sex differentiation.

Answer 6

1. Sexual dimorphism differs across species.
2. sexual dimorphism is related to mating system
3. In polygamous species, males compete for females and females choose their mate

Question 7

What are two pressures on mating

Answer 7

1. Intrasexual selection. When males compete amongst themselves for female attention
2. Intersexual selection. Where females choose males with most appealing traits.

Question 8

Name the behavioral traits and morphological traits of sex differentiation.

Answer 8

Behavioral traits are aggression and solicitation behaviors. Morphological traits are size coloration and ornamentation.

Question 9

What is sexual selection

Answer 9

It’s a form of natural selection where individuals differ in their ability to compete for and or attract potential mates.

Question 10

Name four sexually dimorphic behaviors In human males

Answer 10

• increased body size/strength
• increased aggression
• distinct courtship behavior
• reduced parental care

Question 11

Name in order the stages of sex determination

Answer 11

Chromosomal sex
Gonadal sex
Hormonal sex
Morphological sex
Behavioral sex

Question 12

Briefly describe what happens in chromosomal sex and gonadal sex

Answer 12

In chromosomal sex an X chromosome is received from mothers ovum and and x or y is received from fathers sperm. (Xx female, xy male)
In gonadal sex the SRY region of Y chromosome encoded Testis determination factor to produce testis otherwise ovaries will be produced.

Question 13

Briefly describe what happens in hormonal sex and morphological sex

Answer 13

In hormonal sex the human will either have more of the estrogens steroids or androgen steroids.
In morphological sex the external genitalia will either be smaller for the female or larger for the male

Question 14

How does hormones influence the bipotential gonads

Answer 14

If there is no male hormones the mullarian duct will form which includes Fallopian tubes, uterus and cervix. If male hormones MIS, testosterone and Insi3 are present the wolffian duct will form seminal vesicles and vas deferens.

Question 15

What happens when androgen concentration is low and what happens when it is high?

Answer 15

Masculine genital development when high feminine genital development when low.

Question 16

Explain what Turner syndrome is and what happens

Answer 16

• Damage to x or Y chromosome
• XO genotype
• unambiguously sexed as girls at birth
• ovaries don’t produce steroid hormones
• associated with slow growth, hearing deficits and occasionally intellectual disabilities
• gene imprinting

Question 17

What is the most common cause of anomalous sexual differentiation in human females.

Answer 17

Prenatal exposure to androgens

Question 18

What is the result of the endogenous prenatal exposure to androgens.

Answer 18

Congenital adrenal hyperplasia is when the adrenal glands produce high concentrations of androgens instead of cortisol (moderate to severe masculinization in females)

Question 19

What is Androgen Insensitivity Syndrome

Answer 19

It is an snp on x chomosome which results in non-functional androgen receptor
The xy males are morphologically female and usually regard themselves as female

Question 20

Describe a person with 5a-reductase deficiency

Answer 20

• They are xy males at birth.
• ambiguous genitalia
• usually reared as female
• at puberty high levels of androgens partially masculinity the individual

Question 21

What is hypospadias

Answer 21

Urethra opening at base of penis.

Question 22

Briefly describe two trisomic anomalies

Answer 22

XXY Klinefelter syndrome.
y contains sry and masculinization occurs. It’s associated with sterility, learning disabilities and long limbs.

An XYY individual is sterile, above average height and below average intelligence

Question 23

What does the maternal immunity hypothesis state?

Answer 23

That the number of older biological brother correlated with increased homosexuality in males

Question 24

What is shown in the brains of homosexual men and women?

Answer 24

They display sex-atypical connectivity and asymmetry

Question 25

Describe the positive feedback cycle of the control of ovulation

Answer 25

High levels of estrogen causes the surge center to release a surge of GnRH which stimulates the ant. pit. To release corresponding surges of LH and FSH which stimulates the gonads and causes ovulation.

Question 26

What causes the cycle of ovulation control to go into a negative feedback.

Answer 26

Low levels of estrogens

Question 27

What are environmental endocrine disrupters

Answer 27

DDT, birth control, phthalate, and Chemicals that mimic estrogens, androgens and thyroid hormones.

Question 28

Some example of ED’s adverse affects on health.

Answer 28

Chryptochidism, hypospadias, shorter AGD,

Question 29

What is a morph

Answer 29

Multiple types of the same sex.

Question 30

Explain simultaneous and sequential hermaphroditism

Answer 30

Simultaneous includes ovotestes.

Sequential is either protogynous (female to male) or protandrous (male to female). And it involved change of gonadal type/ function, morphology, behavior.