W3 Genetics, evolution, development & plasticity

Chromosome

A structure in the cell nucleus made of DNA that carries genetic information.

Gene

A segment of DNA that codes for a specific protein.

Sex-linked gene — Genes on sex chromosomes (e.g., X)

Sex-limited gene — Genes present in both sexes but active mainly in one (e.g., Y only appears for male chromosomes).

Distinguish between sex-linked and sex-limited genes

Mutation

A change in DNA sequence due to replication errors, mutagens, or infections.

Point mutation – Small spelling mistakes that affect only one or a few letters in our DNA code [Types of point mutation — Insertion and deletion]

Chromosomal mutation – Entire section of the chromosome can be rearranged or lost

Types of mutation

Phenotype — Observable trait resulted from the genetic makeup.

Genotype — Two alleles that make up the genetic makeup of an organism

Differentiate between genotype and phenotype

Dominant — Only needed one allele to express the observable trait

Recessive — Needed two alleles to express the observable trait

Differentiate between dominant and recessive alleles

Heritability

The extent of passing a trait to the future offspring to inherit

Environment can modify gene expression (e.g., PKU managed by diet).

How can environment affect genetic traits?

Through natural selection of advantageous genetic traits.

How does genetics shape our behavior?

Helping others to increase survival of shared genes (kin selection) or in expectation of return (reciprocal altruism).

What is altruistic behavior in evolutionary psychology?

Proliferation — Production of new cells/neurons

Migration — Movement of newly formed neurons and glia to their locations guided by immunoglobulins and chemokines

Differentiation — Formation of axon then dendrites

Myelination — Production of fatty sheath that covers the axons of some neurons

Synaptogenesis — Formation of synapses between neurons

Stages of neuron development

Promotes survival and growth of axons; lack of it triggers apoptosis.

Role of nerve growth factor (NGF)

Fetal alcohol syndrome

Condition that children are born with if the mother drinks heavily during pregnancy

Interfered with neurons’ stages of development → Blocks excitatory glutamate receptors → Boosts inhibitory GABA receptors → Reduced overall stimulation of the neuron→ Induced apoptosis

How does alcohol affect the brain?

Their brain’s response to rewards and anticipation of rewards increases during teenage years, and continues to do so during adulthood.

Explain why adolescents start to become more impulsive?

Memory and reasoning begin to fade

Genetic and lifestyle factors → May help retain a strong intellect

What happens to cognition in old age and how to maintain cognition?

Stroke

A condition where blood flow to the brain is interrupted.

Ischemic — Caused by blood clot formed within blood vessel in brain

Hemorrhagic — Caused by bursting of blood vessel and internal bleeding

Types of stroke

Edema — Accumulation of fluid in brain → Increased pressure in brain

Disruption of sodium-potassium pump → Accumulation of potassium ions inside neurons → Over-stimulated neuron → Neurons die faster

Effects of stroke

Apathy/Depression

Aggression

Inappropriate behavior — Unable to observe social cues

Pseudobulbar effect — Uncontrollable laughter or crying without emotional regard.

Behavioral changes of stroke

Tissue plasminogen activator (tPA) – Breaks up blood clots (perfect for ischemic strokes)

Blocking glutamate synapses – Avoid overstimulation of neurons to avoid apoptosis

Cooling the brain – Minimize damage (bring down inflammation and overstimulation caused by drugs)

Treatments of stroke

Axon regrowth from collateral sprouting — Fill in vacant synapses

Denervation supersensitivity – Post-synaptic neurons make other cells more sensitive to signals (5 signals needed to activate → only 1 signal is needed to activate)

Recovery mechanisms of brain after stroke