Genetics, Development, and Brain Plasticity Lecture

A set of 150 question-and-answer flashcards covering genetics, brain development, evolution, and neural plasticity concepts from the lecture.

What is the main question addressed in the study of genetics and behavior?

Does human behavior depend on genetics, environmental influences, or both?

How do genes and environment interact in behavior?

Both contribute to shaping behavior; the key question is how much each factor contributes.

What are examples of behaviors influenced by both genes and environment?

Psychological disorders, weight gain, personality, and sexual orientation.

Who was Gregor Mendel?

A 19th-century monk who discovered that inheritance occurs through discrete units called genes.

What are alleles?

Pairs of genes aligned along chromosomes.

What is DNA?

A molecule that composes genes and serves as a model for synthesizing RNA.

What is RNA?

A single-stranded chemical that serves as a template for making proteins.

What do proteins do in the body?

They form body structure and act as enzymes to regulate chemical reactions.

What does it mean to be homozygous for a gene?

Having identical genes on both chromosomes.

What does it mean to be heterozygous for a gene?

Having different genes on each chromosome.

What is a dominant gene?

A gene that shows a strong effect in both homozygous and heterozygous conditions.

What is a recessive gene?

A gene that shows its effect only in the homozygous condition.

Are single-gene traits common in humans?

No, most traits are influenced by multiple genes or expressed only in certain contexts.

What are autosomal genes?

Genes located on chromosomes other than the sex chromosomes.

What are sex-linked genes?

Genes located on the sex chromosomes, especially the X chromosome.

What determines a child’s sex genetically?

The male's sperm—an X chromosome yields a girl (XX), a Y yields a boy (XY).

What are sex-limited genes?

Genes present in both sexes but primarily affect one (e.g., chest hair, breast size).

What is a mutation?

A heritable change in a DNA molecule.

What are microduplications and microdeletions?

Small chromosome segments that are repeated or missing; linked to conditions like schizophrenia.

What is epigenetics?

The study of changes in gene expression without changing the DNA sequence.

What can cause epigenetic changes?

Experience, learning, and environmental factors.

How can monozygotic twins differ genetically?

Due to epigenetic differences that emerge over time.

Can moment-to-moment behavior cause epigenetic effects?

Yes—actions can alter gene expression long term.

What is heritability?

The extent to which genetic differences account for variation in a trait within a population.

Can strong environmental factors reduce heritability?

Yes—they can mask genetic influence.

How do researchers study heredity and environment?

Using twin studies, adoption studies, and gene-behavior correlations.

What is PKU (phenylketonuria)?

A genetic disorder where one can’t metabolize phenylalanine; treatable through diet.

Can genes directly cause behavior?

No, they produce proteins that influence behavioral likelihood under certain conditions.

How can genes indirectly affect behavior?

By altering how others respond to the person (e.g., temperament influencing parenting).

What is evolution?

A change in gene frequency within a population over generations.

What mechanism drives most evolutionary change?

Natural selection.

How do we know species evolved?

From fossil evidence and comparisons among living species.

What are the basic assumptions of evolution?

Offspring resemble parents; mutations and recombinations create variation; some individuals reproduce more successfully.

What is artificial selection?

When humans breed individuals for desired traits.

How did Darwin describe natural selection?

Nature selects individuals whose traits lead to reproductive success.

What is Lamarckian evolution?

The incorrect idea that use or disuse of traits causes their increase or decrease.

Has human evolution stopped?

No—evolution continues.

Does evolution mean improvement?

No—it means change, which isn’t always beneficial.

Does evolution act for the species’ benefit?

No—genes spread by benefiting individuals who reproduce more.

How did brain size evolve in humans?

Possibly due to better nutrition (e.g., cooking), group hunting, and efficient glucose use.

What is evolutionary psychology?

The study of how evolutionary forces shape behavior.

What are examples of behaviors studied in evolutionary psychology?

Color vision, sleep patterns, eating habits, temperature regulation.

What behaviors are harder to explain by natural selection?

Altruism and sexual promiscuity.

What is altruistic behavior?

Helping others at a cost to oneself.

What is group selection?

The idea that cooperative groups out-survive selfish ones—this view is controversial.

What is kin selection?

Helping relatives to increase the survival of shared genes.

What is reciprocal altruism?

Helping someone with the expectation that they’ll help you in return.

What makes reciprocal altruism work?

A good reputation and others’ willingness to cooperate.

What two things influence brain development?

Maturation and learning.

How do neurons refine their connections?

Through development, experience, and pruning of unused connections.

When does the human central nervous system begin to form?

Around the second week of embryonic development.

What forms during early neural development?

A neural tube that becomes the spinal cord and brain.

What does the fluid-filled cavity in the neural tube become?

The central canal of the spinal cord and the brain's four ventricles, filled with cerebrospinal fluid.

How much does the human brain weigh at birth?

About 350 grams.

How much does the brain weigh at one year old?

About 1,000 grams.

What is the adult human brain’s weight?

About 1,200–1,400 grams.

What are the five stages of neuron development?

Proliferation, migration, differentiation, myelination, and synaptogenesis.

What is proliferation?

The production of new neurons and glia early in life.

Where does cell proliferation occur?

In the cells lining the ventricles of the brain.

What are stem cells?

Cells that continue to divide and can become neurons or glia.

What is migration in brain development?

Movement of neurons or glia to their eventual locations.

What guides neuron migration?

Immunoglobulins and chemokines.

What is differentiation in neurons?

The process of forming an axon and dendrites to give a neuron its structure.

What part of the neuron usually develops first?

The axon, followed by dendrites.

What is myelination?

The process where glia form a fatty sheath around axons to speed up transmission.

Where does myelination begin?

In the spinal cord, then the hindbrain, midbrain, and forebrain.

How long does myelination continue?

It occurs gradually for decades.

What is synaptogenesis?

The formation of synapses between neurons.

Does synaptogenesis stop after development?

No, it continues throughout life but slows with age.

Do adults form new neurons?

Yes, especially in the hippocampus and olfactory system.

What are olfactory receptors an example of?

Neurons that are continually replaced throughout life.

What brain area shows new neuron formation in adult mammals?

The hippocampus, which is important for learning.

How long do different neurons live?

Varies—skin cells are mostly new, heart cells last a lifetime, cortical neurons rarely regenerate.

What did Sperry’s experiment with newts show?

Axons follow chemical gradients to find their correct targets.

What principle governs axon target finding?

Axons are attracted to or repelled by specific chemical signals.

What happens when axons reach their target?

They form synapses with multiple cells; some are strengthened and others eliminated.

What determines which synapses are kept?

The pattern of input—active connections are preserved.

What is neural Darwinism?

The idea that successful neural connections survive and unused ones are eliminated.

Who discovered the importance of nerve growth factor (NGF)?

Rita Levi-Montalcini.

What is NGF (nerve growth factor)?

A protein that promotes survival and growth of axons.

What is apoptosis?

Programmed cell death in neurons that fail to make appropriate connections.

What are neurotrophins?

Chemicals, such as NGF, that support neuron survival and activity.

What happens to neurons that don’t receive neurotrophins?

They undergo apoptosis.

What does the adult brain lack?

Neurons that failed to make appropriate connections during development.

What causes thicker visual cortexes in blind people?

Lack of visual input prevents pruning of ineffective neurons.

Why is early brain development vulnerable?

A single mutation or chemical distortion can cause major impairments.

What is fetal alcohol syndrome (FAS)?

A condition caused by heavy prenatal alcohol exposure.

What are symptoms of fetal alcohol syndrome?

Hyperactivity, poor attention, facial abnormalities, heart defects, and intellectual disabilities.

How does alcohol affect fetal neurons?

Reduces glutamate, increases GABA, leading to neuron apoptosis.

What do neurons in different brain regions differ in?

Shape and chemical composition.

Can immature neurons adapt to new areas if transplanted early?

Yes, they take on properties of the new region.

What happens if neurons are transplanted later?

They retain some old properties but also gain some new ones.

What did the ferret rewiring experiment show?

The cortex can adapt to process different types of sensory input.

Can the adult brain reorganize itself?

Yes—experience and learning modify dendrites and synapses.

What are dendritic spines?

Small branches that grow or decline with learning and experience.

What effect does an enriched environment have on rats?

Thicker cortex, more dendrites, and improved learning.

Does physical activity benefit the human brain?

Yes—it enhances neuron expansion and learning.

What is “far transfer”?

The disproven idea that practicing one skill improves general intelligence.

How does the brain of a blind person adapt?

The occipital lobe is repurposed for touch and verbal information.

How does the brain of a deaf person adapt?

The auditory cortex becomes responsive to touch and vision.