Module 53: Sexual Development

Intersex individuals display what variety of characteristics?

Intersex individuals are born with unusual combinations of male and female physical features.

How does fruit fly studies suggest genetic influence on sexual orientation?

Lab experiments have altered a single gene and changed the flies' sexual orientation and behavior.

What are the actual statistics in regards to the percentage of the population who are homosexual or bisexual?

About 2.5% of the population is gay and less than 1% is bisexual. Homosexual men is 3-4% and lesbian women is 1-2%.

How might the mother's immune system play a role in the development of sexual orientation?

After each pregnancy resulting in a boy, the maternal antibodies may become stronger and may prevent the fetal brain from developing in a typical male pattern.

How does twin studies suggest genetic influence on sexual orientation?

Identical twins are somewhat more likely than fraternal twins to share a homosexual orientation.

How is our biological sex determined, and how do sex hormones influence prenatal and adolescent development? • Both sex chromosomes and sex hormones influence development. • Biological sex is determined by the father's contribution to the twenty-third pair of chromosomes. • The mother always contributes an X chromosome. • The father may also contribute an X chromosome, producing a female, or a Y chromosome, producing a male by triggering additional testosterone release and the development of male sex organs. • During puberty, both primary and secondary sex characteristics develop. • Sex-related genes and physiology influence behavioral and cognitive gender differences between males and females.

53.1

What are some of the ways that sexual development varies? • Intersex individuals are born with intermediate or unusual combinations of male and female characteristics. • Research suggests sex-reassignment surgery can be problematic.

53.2

How can sexually transmitted infections be prevented? • Safe-sex practices help prevent sexually transmitted infections (STIs). • Condoms are especially effective in preventing transmission of HIV, the virus that causes AIDS. • A vaccination administered before sexual contact can prevent most human papilloma virus infections.

53.3

What factors influence teenagers' sexual behaviors and use of contraceptives? • Rates of teen intercourse vary from culture to culture and era to era. • Factors contributing to teen pregnancy include minimal communication about birth control with parents, partners, and peers; guilt related to sexual activity; alcohol use; and mass media norms of unprotected and impulsive sexuality. • High intelligence, religious engagement, father presence, and participation in service learning programs have been predictors of teen sexual restraint.

53.4

What has research taught us about sexual orientation? • Sexual orientation is an enduring sexual attraction toward members of one's own sex (homosexual orientation), the other sex (heterosexual orientation), or both sexes (bisexual orientation). • Sexual orientation is not an indicator of mental health. • There is no evidence that environmental influences determine sexual orientation. • Evidence for biological influences includes the presence of same-sex attraction in many animal species; straight- gay differences in body and brain characteristics; higher rates in certain families and in identical twins; exposure to certain hormones during critical periods of prenatal development; and the fraternal birth-order effect.

53.5

FRQ Provide examples of a primary and a secondary sex characteristic for both males and females.

A male primary sex characteristic is the growth of the testes. A male secondary sex characteristic is a lower voice. A female primary sex characteristic is menarche (first period) and full development of external genitalia (ex. uterus). A female secondary sex characteristic is the growth of breasts.

What are some of the most common STI's? Which are on the rise? What age group are the most prevalent in?

Common STI's are AIDS and STDS are on the rise. Age group for STI/STD are 14-19 in females, AIDS are 25-44, HIV causing aids are 25-44. AIDS is a life-threatening, sexually transmitted infection caused by HIV. It depletes the immune system, leaving the person vulnerable to infections.

How does family studies suggest genetic influence on sexual orientation?

Homosexual men tend to have more homosexual relatives on their mother's side than on their father's.

Explain three examples of evidence that suggests a genetic influence on sexual orientation.

Family studies suggest that homosexual men have more homosexual relatives on the mother's side than father's. Twin studies suggest identical twins are more likely to share a homosexual orientation than fraternal twins. Fruit fly studies suggest that an altered single gene changes a sexual orientation and behavior.

In what two ways does biology influence our gender difference?

Genetically: by our differing sex chromosomes (XX = female, XY = male) Physiologically: by our differing concentrations of sex hormones (boys have more testosterone than girls)

X chromosome

The sex chromosome found in both men and women. Females have two X chromosomes; males have one. An X chromosome from each parent produces a female child.

What is the "bottom line" in regards to the influence of environmental factors on sexual orientation?

There is no evidence that environmental influences determine sexual orientation.

sexual orientation

an enduring sexual attraction toward members of either one's own sex (homosexual orientation) or the other sex (heterosexual orientation)

Which of the following has been shown to be the most effective intervention to reduce teen pregnancies? a. Abstinence-only sex education in schools b. Participation in service learning programs c. Increasing guilt related to sexual activity d. Taking a pledge to remain abstinent e. Increased exposure to sexual content in the media

b. Participation in service learning programs

Which of the following is a primary sex characteristic that changes at puberty? a. A growth spurt in height, especially for boys b. Development of breasts for girls c. Full development of external genitalia in both sexes d. Facial hair and deepened voice for boys e. Appearance of pubic and underarm hair in both sexes

c. Full development of external genitalia in both sexes

Which of the following is an example of a primary sex characteristic? a. Nonreproductive traits such as breasts and hips in girls b. Facial hair in boys c. Deepened voice in boys d. Pubic and underarm hair in both sexes e. Reproductive organs in both sexes

e. Reproductive organs in both sexes

secondary sex characteristics

non-reproductive sexual characteristics, such as female breasts and hips, male voice quality, and body hair

primary sex characteristics

the body structures (ovaries, testes, and external genitalia) that make sexual reproduction possible

menarche

the first menstrual period

testosterone

the most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty

puberty

the period of sexual maturation, during which a person becomes capable of reproducing

Y chromosome

the sex chromosome found only in males. When paired with an X chromosome from the mother, it produces a male child.