Transcript Gender Differentiation

The Stork Stopped By, But is
it a Boy or Girl?
From Where Do We Come?
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the stork dropped it through the chimney
found it under a cabbage leaf
went to the store and bought one
baby brought by the police
others?
Early Ideas of Conception
As recently as the 1700s, the exact role played by sperm and egg
was not known:
• mini-people were in sperm and nourished by the woman’s
egg (ova)
• tiny embryos were in the ova and activated by the man’s
sperm
Early Ideas of Conception (con’t)
Cross-cultural beliefs varied considerably as well:
• aboriginal groups in Australia considered intercourse as
preparation for the reception of a spirit baby
• the Mehinaku believed a baby was formed from an
accumulation of sperm
• the Wari’ of the Amazon basin believed that an
accumulation of maternal blood and semen from multiple
partners was necessary to form a baby
Contemporary Ideas of Conception
Fertilization
• Approximately once each month, one of the two ovaries
releases an ovum (ovulation)
• Upon release, the ovum makes its way down the fallopian
tube where it may meet sperm, usually in the upper-third of
the tube (the ampulla)
• There are approximately 100,000,000-400,000,000 sperm
in a single ejaculate. Of those, only 50-60% are motile
• Sperm that do survive surround and attach themselves to
the membrane of the ovum and begin to release enzymes
that breakdown the membrane
Contemporary Ideas of Conception (con’t)
Fertilization
• At some point, one sperm may enter the ovum and other
sperm will be prevented from entering
• All this must happen within approximately 48 hours of
ovulation
• Fertilized ovum now has all the information it needs to
produce the estimated 100 trillion cells of a human
(100,000,000,000,000)
Contemporary Ideas of Conception (con’t)
Cell Division
• mitosis - means by which body (somatic) cells divide and
reproduce identical cells
• meiosis - means by which gamates (germ cells) divide to
produce ova or sperm with 23 chromosomes
Chromosomes
• 23 chromosomes from each parent
• genes - the basic units of heredity
• genes are made of deoxyribonucleic acid (DNA)
Contemporary Ideas of Conception (con’t)
Sex Chromosomes and Autosomes
• autosomes are the first 22 pairs of chromosomes; they are
involved in general body development (e.g., arms, legs,
heart, etc.)
• the 23rd pair are sex chromosomes: X or Y
• XX pairing is a female; XY pairing is a male
• you can distinguish male vs. female by the presence of a
“Barr body” -- condensed, inactive X chromosomes that
look like a clump when stained
Contemporary Ideas of Conception (con’t)
Dominance and Recessiveness
• One gene in each pair of genes (for all chromosomes) is
usually dominant and determines the inherited
characteristic for that gene-pair trait (e.g., brown vs. blue
eyes)
• All the genes on X and Y chromosomes are called sexlinked genes
• Ordinarily recessive traits require a pair of recessive genes
for the recessive trait to appear; in the absence of a pair of
genes, a recessive gene can be manifested.
Are you a Male or a Female?
The process by which gender differentiation occurs is not
so simple as this question suggests.
• Genetic Sex
– the combination of XX or XY chromosomes in the
fertilized egg are “female” and “male” (respectively)
– genetic sex is only the first in a series of stages that
ultimately determines whether we are a “boy” or “girl”
Gonadal Sex
At 8 weeks, the embryo has gonads which contain:
• Müllerian duct system (for female organs -- fallopian
tubes, uterus, and upper vagina)
• Wolffian duct system (for male organs -- epididymis, vas
deferens, seminal vesicles, and ejaculatory duct)
If a Y chromosome is present, H-Y antigen is produced
causing development of testes: otherwise, ovaries develop.
Hormonal Sex
• If testes develop, they
produce testosterone and
Müllerian-inhibiting
substance
• If ovaries develop, the
Müllerian duct system
develops and the Wolffian
duct system atrophies
Genital Sex
Some weeks after the internal structures have been differentiated,
external organs begin to develop:
• formed from the genital
tubercle: the labioscrotal
swelling and urogenital
fold
• develops “male” organs if
dihydrotestosterone (potent
form of testosterone) is
present; otherwise,
develops “female” organs
Secondary Sexual Characteristics
Further sexual differentiation does not change much until the
beginning of puberty. At that time (9 or 10 years of age), the
hypothalamus matures and begins to secrete GonadotropinReleasing Hormone (GnRH) which begins the secretion of FSH
and LH.
Males and females begin to grow pubic hair and, later,
underarm hair, and experience a growth spurt. Both are also
capable of releasing germ cells (i.e., eggs or sperm).
Secondary Sexual Characteristics (con’t)
Females - puberty onset is usually around 9 or 10 years
• ovaries begin to secrete increased levels of estrogen;
follicles grow, the uterus enlarges, and the fallopian tubes
increase in length and width and become straighter
• the vagina, clitoris, and labia grow, the pelvic girdle
widens, and breasts begin to protrude
• “menarche” begins around 12 years, but may vary
normally between 9-16 years
Secondary Sexual Characteristics (con’t)
Males – puberty onset is usually a couple years later than females
• LH stimulates the testes to begin increase production of
testosterone and FSH stimulates sperm production
• testes and penis grow, pubic hair develops, and height and
strength increase, and later facial hair
• larynx grows resulting in a deeper voice
• “nocturnal emissions” begin
Atypical Sexual Differentiation: When
Things Go Awry
In all, nature “adds” something to form males (e.g., testosterone),
otherwise nature delivers a female.
While gender development usually goes according to plan,
abnormalities do occur.
Genetic Abnormalities
Hermaphroditism
Even though an individual may have a normal XX or XY
chromosome pair, abnormal gender differentiation can still occur.
• Hermaphrodite – someone with dual or ambiguous sexual
characteristics with ovarian and testicular tissue (or
ovatestes – undifferentiated gonads)
– are usually genetic females, almost always with a
uterus.
– two-thirds are raised as males because of the enlarged
phallus
– “True” hermaphorditism (as above) is rare. Usually
they have “pseudo-hermaphroditism” – ambiguous sex
characteristics
Genetic Males
• Androgen insensitivity syndrome - genetic males that
usually appear female.
– Wolffian structures (prostate, seminal vesicles, vas
deferens) do not develop
– Müllerian-inhibiting substance prevents female
structures (ovaries, fallopian tubes, uterus) from
developing, but do develop a clitoris and a short vagina
– body does react to estrogen, so breasts develop and
pelvis widens at puberty, but menstruation does not
occur
Genetic Males (con’t)
• Borderline androgen insensitivity syndrome - has some
ability to utilize testosterone
– the “duality” of sexual characteristics is even more
pronounced (e.g., larger penis, partially fused scortum,
testes, etc.)
– Often surgically altered to look more like a female
Genetic Males (con’t)
• Dihydrotestosterone-deficiency (DHT) syndrome - males
lack the enzyme 5 reductase which is needed to transform
testosterone into DHT
– appear more female at birth
– at puberty, however, the penis and scrotum grow, the
voice deepens and they look more male
– poses a problem if they were raised “female”
Genetic Males (con’t)
• Hypospadias – condition in which males are born with an
atypical position of the urethral opening
– opening may be located on glans, corona, along the
shaft, at the junction of the penis and scrotum, or on the
perineum
– surgical reconstruction may be performed to improve
males’ ability to urinate while standing and engage in
unhampered sexual functioning
Genetic Males (con’t)
• Swyer Syndrome – mutation of the SRY (Sex-determining
Region of Y), resulting in testicular development failure
– testosterone is not produced and Müllerian-inhibiting substance
is absent
– Müllerian ducts develop into internal female organs;
nonfunctional “streak ovaries” are present
– lack of ovaries results in failure to develop secondary sexual
characteristics, including menstruation
– administration of estrogen and progesterone permit
development of breasts, uterus, and regulation of menstruation
– administration of estrogen and progesterone permit
development of breasts, growth of uterus, and regulation of
menstrual cycle
Genetic Females
• Congenital Adrenal Hyperplasia (Androgential
syndrome) - genetically transmitted malfunction of the
adrenal glands which produces excess levels of androgen
– excess masculinizes the external genitals – vagina may
not be open and clitoris is often enlarged
– if detected at birth, surgery can correct this and
cortisone is administered to reduce the output of
androgens
– child will develop as a normal female
Genetic Females (con’t)
• Progestin-induced masculinization - to prevent
miscarriages, some women were given progestagens
(synthetic progestins)
– depending on the levels used, some XX females
showed normal female genitals, some masculinized,
and some ambiguous
– internal organs developed normally as female
– if masculinization occurs and is identified at birth,
surgery and hormone treatment will result in normal
female development
• Progestin-induced masculinization (con’t)
– if not, they will develop breasts and menstruate at puberty
and then find out they were really a genetic female
– treatment will result in normal female development
– person must choose to become “male” or “female”
Gender Identify and Gender Role
“What are males and females like?”
Males
physically strong
aggressive
independent
dominant
Females
physically weak
nonaggressive
dependent
submissive
Gender stereotypes - beliefs, that may or may not be accurate,
based on one’s gender.
Gender differences - reliable differences between the average
male and average female as determined by research.
Gender Identify and Gender Role (con’t)
When we consider such behaviors and traits, we find that men and
women “overlap,” whether they are stereotypes or differences.
Grip
Strength
Female Male
Given such overlap of traits and behaviors, “What does it mean
to be ‘male’ or ‘female?”
Gender
We could, initially, point to gender – a person’s biological
“maleness” or “femaleness.”
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genetic (chromosomal) gender: XX (female) XY (male)
gonadal gender: ovaries (female) or testes (male)
hormonal gender: relative “mix” of estrogens and androgens
genital gender: clitoris, vagina, (female) or penis, scrotum
(male)
Usually one’s gender is unambiguous, although hermaphroditism
(intersexuality) can occur.
Gender Identity
Many psychologists believe a more useful way to approach our
question would be to examine the concept of gender identity:
one’s psychological sense of being “male” or “female.”
• Gender assignment - identifying the gender of a newborn
(e.g., “It’s a girl!”)
• From that point on, a process begins that results in one’s
gender identity: gender role socialization
Gender Role Socialization
Cultures differ in what is believed to be appropriate gender
roles: the traits and behaviors expected of males and females in
a given culture. The Tchambuli gender roles, for example, are
reversed with our culture’s.
Gender role socialization is the training of appropriate gender
roles. The “teachers” of gender roles are many:
• Parents: mothers and fathers perceive and treat their sons
and daughters differently
– girls are seen as softer, smaller, more fragile, etc., are
spoken to more often, and given “girl” toys
– boys are seen as stronger, better coordinated, tougher,
etc., are played with more roughly, given “boy” toys
Gender Role Socialization (con’t)
• Peers: “friends” exert considerable pressure to conform by
reinforcing “correct” behavior and withholding or
punishing “incorrect” behavior. Have you heard these?
– You can’t play ball with us, you’re a girl.
– Ooh! Ooh! Boys. Yuck! Let’s run!
– Well my daddy can beat your daddy.
– Johnny is a sissy. Johnny is a sissy
• School: schools provide another context for gender role
socialization
– there may be male/female dress codes
– different physical education activities
– different classes (e.g., sewing, home ec. versus metal
shop , woodworking)
Gender Role Socialization (con’t)
• Mass media: TV, film, magazines are filled with gender
roles
What kinds of examples can you give and how do you think
gender roles in the media have changed over time?
Gender Role Identification
Gender role identification: the process by which genderappropriate traits and behaviors are incorporated into one’s
personality.
An individual was viewed as suffering from “gender role
confusion” if the individual exhibited traits or behaviors of the
opposite gender.
Carl Jung’s concepts of animus (males archetype) and anima
(female archetype) were resurrected, and the position of
polarity between gender roles (either/or) came under attack.
Androgyny
Sandra Bem developed a gender identify measure called the
“Bem Sex Role Inventory.”
Androgynous - people who describe themselves equally with
feminine and masculine traits and behaviors.
Gender-typed individuals were those who describe
themselves predominantly with stereotypical gender traits and
behaviors.
It is now the prevailing view that androgynous individuals are
perhaps more well-adjusted in that they are able to respond
more flexibly in a variety of situations (e.g., be comforting or
assertive as necessary).