Unit 4 Genetics, Evolution, Development & Plasticity Flashcards
What two factors influence everything you do?
Your genes and your environment
What did researchers find about facial expressions in people born blind?
They were remarkably similar to those of their sighted relatives
What does the term ‘Mendelian Genetics’ refer to?
Inheritance occurs through genes, units of heredity that maintain their structural identity
What are the pairs of genes aligned along?
Chromosomes
What is the classical definition of a gene?
Part of a chromosome composed of the double-stranded molecule deoxyribonucleic acid (DNA)
What does a strand of DNA serve as a template for?
The synthesis of ribonucleic acid (RNA) molecules
What type of RNA serves as a template for the synthesis of protein molecules?
Messenger RNA
What determines the order of amino acids in a protein?
The order of bases along an RNA molecule
what are the two ways genes can present as
- Homozygous
- Heterozygous
What is a dominant gene?
A gene that shows a strong effect in either the homozygous or heterozygous condition
What is a recessive gene?
A gene that shows its effects only in the homozygous condition
How many genes contribute to variations in eye color?
At least 10 genes
What are sex-linked genes?
Genes on the sex chromosomes (X and Y in mammals)
What defines a female mammal in terms of sex chromosomes?
Two X chromosomes
What is an example of a human sex-linked gene?
The gene that controls red-green color vision deficiency
What are sex-limited genes?
Genes present in both sexes but active mainly in one sex
What is mutation in genetics?
A heritable change in a DNA molecule
What kind of mutation involves part of a chromosome appearing twice or not at all?
Duplication or deletion
What does epigenetics study?
Changes in gene expression
What can modify gene expression?
Various experiences and environmental factors
What does heritability indicate?
The extent to which observed differences among individuals depend on genetic differences
What is the difference between monozygotic and dizygotic twins?
Monozygotic twins share the same genes; dizygotic twins do not
What evidence do researchers use to determine heritability?
- Comparison of monozygotic and dizygotic twins
- Studies of adopted children
- Examination of virtual twins
gene identification
Fill in the blank: A dominant gene shows a strong effect in either the _______ or _______ condition.
homozygous, heterozygous
True or False: All RNA molecules code for proteins.
False
What can severe traumatic experiences in early childhood affect?
Methylation of many brain genes
What is a key role of enzymes in the body?
Regulate chemical reactions
What happens to the expression of certain genes during puberty?
Certain genes that had been almost silent become much more active
What is the effect of maternal malnutrition on offspring?
Alters the expression of certain genes to conserve energy
What is implied by any genetic similarity between behaviors?
Environmental influences
Behavioral differences suggest genetic influences.
What do studies of adopted children indicate about hereditary influence?
Tendency to resemble biological parents
Evidence is not always decisive due to prenatal environment.
What types of behaviors have researchers found significant heritability for?
- Loneliness
- Neuroticism
- Television watching
- Childhood misbehavior
- Social attitudes
- Cognitive performance
- Educational attainment
- Speed of learning a second language
Religious affiliation has not shown significant heritability.
What does heritability of a trait depend on?
The specific population
Example: Alcohol abuse shows moderate heritability in the U.S.
What is the candidate gene approach?
Testing hypotheses linking specific genes to behaviors
Example: Gene linked to serotonin transporter and depression.
What is a genome wide association study?
Examines all genes comparing two groups
Risks include false positives and misleading results in diverse samples.
What are some well-supported findings from behavioral genetics?
- Almost everything in psychology shows genetic influence
- Nothing in psychology has 100% heritability
- Heritability depends on many genes with small effects
- Stability of behavior over age is due to genetics
Few identified genes with major effects exist.
What are potential reasons for not locating strong links between genes and behaviors?
- Many genes exert small effects
- Microduplications or microdeletions
- Rare mutations with large effects
- Epigenetic effects
These factors complicate the understanding of genetic influences.
What is phenylketonuria (PKU)?
A genetic inability to metabolize phenylalanine
Can lead to brain development issues if untreated.
How can environmental interventions modify PKU?
Strict low-phenylalanine diet
Success shows that heritable traits can be modified.
What is the relationship between genes and behavior?
Genes produce proteins influencing behavior through complex interactions
Genes can influence behavior indirectly via environmental interactions.
What did Charles Darwin prefer to call evolution?
Descent with modification
Emphasizes changes without implying improvement.
What are the two questions about evolution?
- How did some species evolve?
- How do species evolve?
These address evolutionary relationships and mechanisms.
What is artificial selection?
Selecting individuals with desired traits for breeding
Used in agriculture and animal breeding.
What is a common misconception about evolution regarding the use of traits?
Use or disuse of traits causes evolutionary changes
This idea is rooted in Lamarckian evolution, which lacks evidence.
Does modern medicine stop human evolution?
No, evolution depends on reproduction, not just survival
Genes can still spread if certain individuals reproduce more.
What does evolution improve according to its definition?
Fitness
Fitness is defined by the number of gene copies that endure in later generations.
Does evolution benefit individuals or species?
It benefits the genes
Genes use individuals to reproduce themselves.
What is a misconception about lemmings and evolution?
Lemmings jump off cliffs to control population
This would disadvantage the ‘self-sacrificing’ gene.
histones
proteins that bind DNA into a shape that resembles a string would around a ball
what happens when Acetyl groups are add and removed within a cell (epigenetics - how does the experience modify gene expression)
added -> loosens dna and gene is turned on
removed -> tightens dna and gene is turned off
what happens when methyl groups are added and removed within a cell (epigenetics - how the experience modifies gene expression)
added: gene is turned off
removed: gene is turned on
methylation
biochemical process where Methyl groups are added to a molecule such as DNA/ When added to DNA the gene is turned off/removed gene is turned on
common misunderstandings of evolution
use/disuse changes traits (based on Lamarckian evolutionary theory - traits evolve only through inheritance genetic change)
Humans stopped evolving (evolution depends on reproductive success, not just survival)
Evolution = improvement (evolution is improved fitness, not necessarily moral or social betterment
Evolution favors species (false, evolution favors genes, behaviour that benefit gene carriers spread)
evolutionary psychology
focuses on how behaviors evolved (via natural selection)
altruistic behaviour
an action that benefits someone other than the action (in humans - charity, in non humans, rare)
explanations for altruism
kin selection, reciprocal alturism, and group selection
kin selection
selection for a gene that benefits the individuals relatives (bc they share your genes)
reciprocal altruism
idea that individuals help those who will return the favour (people help those they see helping others)
group selection
cooperative groups survive better than selfish/less cooperative ones
What are homeobox genes?
Genes found in vertebrates, insects, plants, fungi, and yeast that regulate gene expression and anatomical development.
They control body orientation and mutations can lead to deformities and brain disorders.
When does the human central nervous system begin to form?
At 2 weeks of embryo development.
The neural tube forms, leading to the development of the hindbrain, midbrain, and forebrain.
What occurs at 7.5 weeks of embryo development?
Muscle movements start, limited to stretching muscles.
Spinal cord activity drives muscle movement before sensory organs are functional.
What is the weight of the human brain at birth?
350 grams.
By the end of the first year, the brain weighs about 1000 grams.
What areas of the cortex mature early?
Primary sensory areas, including vision and hearing.
These areas establish connections to the thalamus early in development.
Which part of the brain shows significant development in the first couple of years?
Prefrontal cortex.
It is involved in attention, working memory, and decision-making.
What is the adult weight range of the human brain?
1200-1400 grams.
This weight is reached after several years of development.
What is synaptogenesis?
The formation of synapses that give a neuron its distinctive properties.
It begins before birth and continues throughout life.
What is myelination?
The process by which glia produce insulating fatty sheaths that accelerate transmission in vertebrate axons.
It begins in the spinal cord and continues into adulthood.
What traditional belief did Cajal hold about neuron formation?
That vertebrate brains only formed neurons during embryological development or early infancy.
This belief has been challenged by recent findings.
Which brain area is known for forming new neurons in both birds and mammals?
Hippocampus.
New neurons support learning and memory formation.
What is the C-14 Radioactive Isotope Method used for?
To track the age of cells based on carbon-14 concentration in their DNA.
This method revealed insights into neuron turnover rates in different tissues.
What happens to neurons that do not receive nerve growth factor (NGF)?
They undergo apoptosis (programmed cell death).
NGF promotes the survival and growth of axons.
What is fetal alcohol syndrome (FAS)?
A condition resulting from prenatal alcohol exposure, leading to various cognitive and physical impairments.
It can cause thinner cerebral cortex and lasting effects into adulthood.
How does alcohol affect developing neurons?
It disrupts neuron proliferation, migration, differentiation, and synaptic transmission.
Alcohol alters neurotransmitter activity, promoting neuron death.
What is the role of neurotrophins?
They promote the survival and activity of neurons.
BDNF (brain derived neurotrophic factor) is an important neurotrophin related to depression.
What is the principle of neural Darwinism?
Competition among axons to establish appropriate synapses.
More appropriate synapses are strengthened while others are eliminated.
What did Rita Levi-Montalcini discover about neuron formation?
Muscles do not determine the number of axons formed, but rather how many survive.
This led to understanding that the nervous system overproduces neurons.
What are the effects of maternal stress on offspring?
Influences offspring’s brain and behavior, leading to more academic and social difficulties.
Stressed mothers may groom less, resulting in fearful offspring.
What happens to early-stage transplanted neurons?
They fully adopt the properties of the new cortex location.
This shows the adaptability of neurons during development.
What did the ferret experiment demonstrate about sensory input?
It can guide the development and specialization of cortical areas.
Researchers rerouted optic nerves to auditory areas, showing functional plasticity.
How do adult neurons change shape?
Through growth, retraction, or disappearance of dendritic branches.
This plasticity allows adaptation to new experiences.
What is brain plasticity?
The nervous system can remodel in response to experience.
How do adult neurons change shape?
Particularly in peripheral dendritic branches.
What percentage of dendritic spines change within a month?
~6%.
What is linked to learning in the context of dendritic spines?
Changes in spines = synapse turnover.
What are the effects of enriched environments on rats?
- Developed thicker cortex
- More dendritic branching
- Improved learning.
What difference was observed between wild-caught rats and lab rats?
Wild rats had more neurons in visual areas, fewer in auditory areas.
What does stimulating environments promote across species?
Axon/dendrite sprouting.
What is a significant benefit of using a running wheel for rodents?
Boosts growth of axons/dendrites and learning.
How do enriched environments affect humans?
Effects are less clear; better outcomes seen in normal environments vs. minimal-care orphanages.
What is ‘far transfer’ in learning?
Improvement on unrelated tasks.
What is ‘near transfer’ in learning?
Improvement on similar tasks.
Is there strong evidence for far transfer?
No, evidence shows far transfer is weak.
What cognitive skills do brain puzzles improve?
Puzzle-specific skills, not general cognition.
What cognitive benefits have been associated with complex 3D video games?
Potential cognitive benefits after prolonged play.
What are the effects of general brain training?
Limited/temporary improvements.
What happens to the brain when sensory systems are impaired?
The brain can reorganize.
How do blind individuals demonstrate enhanced sensory attention?
Increased attention to touch and sound.
What is the outcome of tactile tasks for blind individuals?
They outperform sighted individuals.
What happens to the occipital cortex in blind individuals during touch-based tasks?
It becomes active.
What is the effect of music training on the auditory cortex?
Musicians show stronger auditory cortex responses (about 2x).
What brain changes are associated with musicians?
- Enlarged brain areas related to hearing and finger control
- Enhanced subcortical responses to music and speech.
How does early music training affect the brain?
Earlier training leads to greater effects.
What is focal hand dystonia?
A disorder where one or more fingers are in constant contraction.
What is a cause of focal hand dystonia?
Brain-based overlap in brain maps of fingers.
What behavioral traits are associated with adolescence?
- More impulsive than adults
- Prefer immediate rewards.
How does the prefrontal cortex relate to impulse control in adolescents?
It is less mature, correlating with impulse control.
What happens to cognitive abilities in old age?
- Memory and reasoning generally fade
- Loss of synapses.
What misconceptions exist about cognitive decline in older adults?
Not all older adults experience significant decline; many retain sharp cognitive abilities.
What protective factors can boost cognitive function in older adults?
- Exercise
- Engaging in mentally stimulating activities.
What happens to the hippocampus with age?
It shrinks, leading to memory declines.
What is the effect of blood transfusion studies on learning and memory in mice?
- Old to young: impairs plasticity and learning
- Young to old: improves dendritic spine density and learning.
stages in neuron development
proliferation
migration
differentiation
myelination
proliferation
Production of new cells, occurring mainly in the ventricles of the brain.
stem cells
undifferentiated cells that divide and produce daughter cells that develop more specialized properties)
migration
moving of cells
differentiation
to develop the axon and dendrites, and synapses that give a neuron its distinctive properties
synaptogeneis
formation of synapses
myelination
process by which glia produce the insulating fatty sheaths that accelerate transmission in many vertebrate axons
tectum
visual area of the brain
neural Darwinism
principle of competition among axons
nerve growth factor
a protein that promotes the survival and growth of axons in the sympathetic nervous system and certain axons in the brain
apoptosis
programmed cell death
neurotrophins
chemical that promotes the survival and activity of neurons (i.e. NGF, BDNF)
DBNF
brain derived neurotrophic factor
gastrulation
crucial embryonic stage, errors here are fatal
fetal alcohol syndrome
a condition resulting from prenatal exposure to alcohol and marked by characteristics like: hyperactivity, impulsiveness, decreased alertness, varying degrees of cognitive impairment
what do the early, mid, and later stages of alcohol damage look like
early -> dirupts neuron proliferation (fewer neurons produced)
mid -> impairs neuron migration (neurons moving to correction location) and differentiation (how neurons develop functions)
later -> impairs synaptic transmission
how does alcohol prevent developing neurons from being stimulated
Alters NT activity and promotes apoptosis by inhibiting glutamate receptors (helps neurons stay active, neurons die due to decrease in excitation) AND enhancing GABA receptors (gaba is inhibitory, and slows activity, further suppresses neural activity)
how does alcohol continue to cause harm in the fetus after it has left the system?
○ Neurons adapted by building extra glutamate receptors (to compensate suppression)
○ When alcohol leaves, glutamate overexcites receptors
Causes excess sodium and calcium to flood cells, poisoning the mitochondria
far transfer
improvement on unrelated tasks
near transfer
improvement on similar tasks
What are common causes of brain damage?
Tumors, infections, exposure to radiation or toxic substances, degenerative conditions like Parkinson’s and Alzheimer’s.
What is a closed head injury?
A sharp blow to the head that does not puncture the brain.
What is the most common cause of brain damage in young people?
Closed head injury.
What does the duration of confusion and memory loss predict?
Strong predictor of long-term outcome.
What percentage of closed head injury cases require hospital treatment?
7-8%.
What are the causes of damage after a closed head injury?
- Rotational forces that drive brain tissue against the inside of the skull
- Blood clots that interrupt blood flow to the brain.
How do woodpeckers avoid brain injury despite high-speed impacts?
- Use light taps before hard strike
- Hard strike is straight and controlled
- Rigid neck and spongy skull bones act as natural shock absorbers.
What implications do woodpeckers’ adaptations have for humans?
Better helmet design, tuck chin to chest in crashes.
What is a stroke?
Temporary interruption of normal blood flow to a brain area, also known as a cerebrovascular accident.
What is the common cause of brain damage in older people?
Stroke.
What is ischemia?
Result of a blood clot or other obstruction in an artery.
What happens to neurons during ischemia?
They are deprived of blood and lose much of their oxygen and glucose supplies.
What is hemorrhage in the context of stroke?
Result of a ruptured artery.
What are the effects of hemorrhage on neurons?
Flooding with blood and excess oxygen, calcium, and other chemicals.
What is edema?
Accumulation of fluid that increases pressure on the brain and probability of additional strokes.
What is denervation supersensitivity?
Increased sensitivity to neurotransmitters by a postsynaptic neuron after loss of input.
What is the role of tissue plasminogen activator (tPA) in stroke treatment?
It is a drug that breaks up blood clots, improving outcomes for ischemia if administered quickly.
What challenges exist in determining if a stroke is ischemic or hemorrhagic?
Only an MRI can determine this, but time is limited for treatment.
What are some other treatment attempts for stroke?
- Decrease stimulation by blocking glutamate synapses
- Cooling the brain
- Antioxidants
- Antibiotics
- Albumin
- Treatments affecting the immune system.
What effects do cannabinoids have on stroke damage in animals?
Reduce stroke damage by reducing glutamate release, having anti-inflammatory effects, and altering brain chemistry protectively.
What is the general recovery process following a brain injury?
Surviving brain areas reorganize and increase activity.
What is diaschisis?
Decreased activity of surviving neurons after damage to other neurons.
What was the outcome of Feeney’s experiment with rats and cats after cortical damage?
Amphetamine increased dopamine and enhanced behavioral recovery.
What is axon sprouting?
After a cell loses input from an axon, it secretes neurotrophins inducing other axons to form new branches.
What does denervation supersensitivity compensate for?
Lost input from active synapses.
What is the phantom limb phenomenon?
Continuing sensation of an amputated body part.
What can trigger phantom sensations in amputees?
Stimulation of adjacent body parts.
What is the significance of artificial limbs in relation to phantom pain?
They can help displace abnormal connections that cause phantom sensations.
What is the effect of therapy on recovery from brain damage?
It encourages learning to make better use of abilities that were spared.
What are deafferented limbs?
Limbs that have lost afferent (sensory) input but still have motor nerve connections.
What is a key implication for stroke recovery?
Forcing patients to use the weaker limb by preventing use of the normal limb.
What factors can make recovered behaviors vulnerable?
- Alcohol
- Exhaustion
- Stress
- Aging.
deafferented
lost afferent (sensory) input but motor nerves still connect to muscles in the limb
homozygous
having two identical gens for a given characteristic, identical genes on both chromosomes
heterozygous
different versions of a gene, unmatched pair
three types of genes
dominant, recessive, and intermediate
