Exam 2 CHAPTER 10

• Study notes for Chapter 10, Biology and Gender examines if biological sex differences create psychological gender differences, and if women’s behavior is controlled by biology

Sex Chromosomes

• Male sex chromosomes are XY, while female sex chromosomes are XX
• Egg cells always contribute an X chromosome
• Sperm cells contribute either an X or a Y chromosome, determining the sex of the offspring

Sex-linked Trait

• Sex-linked trait refers to a trait that is determined by a gene located on a sex chromosome, typically the X chromosome

SRY Gene

• SRY gene's purpose is to initiate male development
• SRY gene triggers the development of the testes

X-Chromosome Inactivation

• X-chromosome inactivation is the process by which one of the two X chromosomes in female mammals is randomly turned off
• X-chromosome inactivation occurs to ensure that females, like males, have only one functional copy of the X chromosome in each cell

Genomic Imprinting

• Genomic imprinting is the epigenetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner

Epigenetics

• Epigenetics refers to changes in gene expression that do not involve alterations to the DNA sequence itself
• Epigenetics demonstrates that genes are not necessarily destiny

Sex Differences in Basic Physiological Processes

• Metabolism: Males typically have a higher metabolic rate than females
• Drug Absorption: Differences exist between males and females
• Pain Sensitivity: Women report greater pain sensitivity than men

Major Sex Hormones

• Major male sex hormones include androgens, such as testosterone
• Major female sex hormones include estrogens and progestins

Organizing and Activating Effects

• Organizing effects of hormones occur prenatally and during puberty, and are responsible for the development of sex-specific anatomy and physiology
• Activating effects of hormones occur in adulthood, when hormones activate certain behaviors
• Animal research indicates that early exposure to testosterone masculinizes behavior

Prenatal Development

• Prenatal development begins at conception with the fusion of sperm and egg
• If the SRY gene is present and functional, the fetus will develop testes; otherwise, the fetus will develop ovaries
• The presence or absence of testosterone determines the development of male or female genitalia

Intersexuality

• Intersexuality refers to conditions in which a person is born with sex characteristics that do not fit typical definitions of male or female

Congenital Adrenal Hyperplasia (CAH)

• CAH is caused by a genetic defect that results in the overproduction of androgens by the adrenal glands
• In females, CAH can lead to masculinization of the genitalia

Turner Syndrome

• Turner syndrome is a genetic disorder that affects females
• Turner Syndrom happens when they are born with only one X chromosome
• Turner Syndrome results in a failure to develop secondary sexual characteristics and infertility

Androgen-Insensitivity Syndrome (AIS)

• AIS is a genetic condition that affects males
• AIS makes them unable to respond to androgens
• AIS results in a female phenotype despite having XY chromosomes

5-Alpha-Reductase Deficiency

• 5-Alpha-Reductase Deficiency is a genetic condition that affects males
• 5-Alpha-Reductase Deficiency impairs the conversion of testosterone to dihydrotestosterone (DHT)
• 5-Alpha-Reductase Deficiency results in incomplete masculinization of the external genitalia at birth

Activating Effects of Sex Hormones During Adolescence

• During adolescence, sex hormones activate the development of secondary sexual characteristics
• During adolescence sex hormones affects sexual behavior and reproductive function

Effects of Testosterone

• In males, testosterone promotes muscle growth
• In males, testosterone promotes bone density, and the development of secondary sexual characteristics
• In females, testosterone contributes to bone density and muscle strength

Sex Differences in the Brain

• Hypothalamus: Certain nuclei in the hypothalamus differ in size between males and females
• Corpus Callosum: Some studies suggest that the corpus callosum is larger in females than in males, but this finding is inconsistent
• Brain Size: On average, males have larger brains than females, but this difference does not necessarily indicate differences in cognitive ability

Lateralization

• Lateralization refers to the specialization of function in one hemisphere of the brain relative to the other
• Split visual field tasks presents stimuli to either the left or right visual field
• Split visual field tasks assesses processing in the contralateral hemisphere
• Dichotic listening tasks presents different auditory stimuli to each ear simultaneously
• Dichotic listening tasks tests for hemispheric dominance for language processing

Cognitive Crowding Hypothesis

• Cognitive crowding hypothesis suggests that when both hemispheres are involved in the same function, cognitive abilities may be reduced
• Cognitive crowding hypothesis explains why sex differences in verbal ability and spatial ability are small or nonexistent

Neural Plasticity

• Neural plasticity refers to the brain's ability to reorganize itself by forming new neural connections throughout life
• Neural plasticity allows the brain to adapt to changing environmental conditions and experiences

Brain "Mosaic"

• The brain mosaic concept posits that individual brains are composed of unique combinations of features, some of which are more common in one sex or the other
• The brain mosaic rejects the idea of a binary sex difference in brain structure

Brain Changes in Transwomen Receiving Hormone Therapy

• Research has shown that hormone therapy in transwomen can lead to changes in brain structure, including decreases in gray matter volume in some regions and increases in others
• These changes suggest that brain structure is not fixed and can be influenced by hormonal environment