🏙️ Where this fits in Brain City
GENES carry instructions → instructions help make PROTEINS → proteins help build/run the BRAIN & NERVOUS SYSTEM → ENVIRONMENT changes how the system develops and which genes are expressed → across GENERATIONS, selection changes which alleles become common → behavior reflects BOTH biology and experience.
Connection forward: Week 2 explains where some of Brain City’s biological building instructions come from. Week 3 then follows how neurons send electrical messages, and Week 4 follows how neurons communicate across synapses.
🧠 Main memory: Genes are instructions, not destiny. Heritability is about differences in a population, not a percentage of you.
👀 Visual Connections
1. Gene expression chain
DNA → mRNA → PROTEIN → structures / enzymes → brain & behavior
2. Twin-study logic
Monozygotic: essentially 100% shared genes → compare with → Dizygotic: about 50% shared genes.
3. Heritability is NOT a person pie
Wrong picture: “I am 70% genes and 30% environment.”
Course picture: Heritability describes variability between people in a population under particular environmental conditions.
4. Evolution chain
Inherited variation → different reproductive success → alleles represented differently in next generation → allele frequencies change over generations
📚 Teach It — Simple → College Terms → Source
🖥️ Professor Slides → Course Material
The important Week 2 slide content is rebuilt here as study material. The full read-through professor-slide deck is also in Course Materials.
Nature AND nurture
Behavioral traits reflect interaction between genes and environment; behavior genetics estimates contributions to variability.
Twin studies + heritability
MZ ≈100% genes, DZ ≈50%; equal-environment assumption; heritability describes population variability.
Genes → proteins
Genes are DNA segments; gene expression follows DNA → mRNA → protein; proteins build structures and act as enzymes.
Alleles + polygenic traits
Homozygous/heterozygous, dominant/recessive, sex-linked/sex-limited; most traits are polygenic.
Evolution + selection
Evolution changes allele frequencies; natural/ecological, sexual, and artificial selection affect reproductive success.
Evolutionary psychology + altruism
Functional/evolutionary explanations; kin selection and reciprocal altruism are central course examples.
📘 Textbook Practice Questions
One question at a time. Questions and answer choices reshuffle each time you start/reload practice.
🧪 Week 2 Practice Quiz
Additional practice generated only from your Week 2 textbook, professor slides, and lecture transcript. One question at a time, randomized each practice.
👨🏾🏫 Professor Quiz
Reserved for the actual Week 2 professor quiz when you provide it. Generated practice questions stay separate.
🧠 Tap-to-test college vocabulary
Tap a term to open it. Say what it means first, then check the course definition.
🔗 How It All Connects
DNA contains genes → genes have alleles → gene expression helps make proteins → proteins help build and run the nervous system → environment interacts with genes and can influence expression → these interactions contribute to behavioral differences → inherited variation affects reproductive success → across generations allele frequencies can change → evolution.
Into Week 3: Week 2 explains the biological instructions and variation behind Brain City. Week 3 zooms into the neurons those biological systems build and asks how one neuron creates and sends an electrical message. Into Week 4: after that action potential reaches the terminal, the story continues at the synapse.
🎯 Full Breakdown — What You Should Remember
Put the whole Week 2 story together: genes are DNA instructions that help make proteins, but behavior is not genes alone—genes and environment work together. Alleles are different versions of genes, most behavioral traits are polygenic, and heritability describes differences within a population rather than how “genetic” one person is. Environmental experiences can influence gene expression through epigenetic processes. Across generations, inherited variation and differences in reproductive success can change allele frequencies, which is evolution. Natural, sexual, and artificial selection describe different ways reproduction can be shaped, while evolutionary psychology asks how behavior may connect to adaptive or functional history.
Nature + nurtureBehavior reflects interaction between genetic and environmental influences.
Genes → proteinsGenes are DNA instructions; DNA information is used through mRNA to make proteins.
AllelesAlleles are versions of genes. Homozygous = same; heterozygous = different.
Most behavioral traitsMost are polygenic and environmentally influenced, not controlled by one gene.
Twin studiesMonozygotic twins share essentially 100% of genes; dizygotic twins about 50%.
HeritabilityIt describes variation in a population. It does not tell you what percentage of one person is genetic.
EpigeneticsEnvironment can alter patterns of gene expression without rewriting the DNA sequence.
EvolutionChange in allele frequency in a population over time.
FitnessIn this course context, evolutionary fitness is tied to reproductive success.
SelectionNatural/ecological, sexual, and artificial selection can change which traits/alleles are represented in later generations.
Evolutionary psychology + altruismCourse material connects evolutionary/functional explanations with kin selection and reciprocal altruism.