Unit 3: Genetics & Evolutionary Foundations Of Behaviour (Chapter 3) Flashcards
Nature
The result of our genetic makeup.
Nurture
The environment and experiences that shape us.
Genome
Complete set of genetic material; the “blueprint” for making & maintaining an organism.
DNA
Molecule that carries genetic information, organized and packaged within chromosomes.
- Most human body cells carry 2 pairs of 23 chromosomes (46 total).
- Exception: reproductive cells, which carry 23.
Gene
Segment of DNA that codes for a particular protein. Humans have 2 versions (alleles) of each gene, 1 from each parent.
Genotype
Made up of 2 alleles for a particular gene. An individual may be homozygous for gene (NN or nn) or heterozygous for gene (Nn).
Phenotype
Observable characteristics of an individual, produced by interaction of genotype and environment.
Recessive alleles
Determine phenotype only when individual is homozygous for gene.
Not all genes act in dominant/recessive fashion
Dominant alleles
Determines phenotype regardless of whether an individual is homozygous or heterozygous for gene.
Not all genes act in dominant/recessive fashion
What do genes code for?
Genes code for proteins, which contribute to phsycial structures & fuctons of the body, including the brain. Multiple genes are involved in giving rise to complex mental states, behaviours, and traits.
Ex: Code proteins and enzymes involved in production of chemical “messengers” and their receptors that allow neurons to “talk” to each other.
Behavioural genetics
Establishing the degree of heritability for a trait. (I.e. How much variability for a trait can be attributed to genes.)
Evolutionary psychology
Examining why certain genetically-encoded behaviours & traits emerged.
Candidate gene studies
Compare individuals with the candidate gene with individuals without on a given trait or disorder.
Limitations of candidate gene studies
- Typically correlational in nature (other factors, like other genes, cannot be ruled out).
- Underestimate biological complexity of multifaceted traits & behaviours.
- Many promising candidate gene studies have failed to replicate.
Gene knockout
Remove or deactivate gene; modify it so it no longer produces its typical proteins.
Gene knockdown
Make gene less active; “turn down” its volume.
Ex: Mice who don’t miss mom study; genetic knockdown of the u-opioid receptor = defecits in attatchment.
Genome-wide association studies (GWAS)
Instead of looking at single gene (or small set of genes), scan entire genome & look for associations with particular phenotype. This may allow us to identify variants missed through candidate gene approaches.
GWAS Limitations
- Run the rish of false positives,
- Biological relevance often not clear.
- Correlational.
How do genes shape our environments?
Genes shape behavioural tendencies & preferences, and thus environments individuals seek out.
Ex: Individuals genetically predisposed to anxiety may seek less stressful professions.
Environments moderate the impact of genes
The effect of a gene on the manifestation of a particular phenotype may depend on context. In statistical terms, context moderates impact of gene (can also say that genes and environments interact to produce outcomes). Not all genes read all the time, and environment affects which ones are turned “on” and “off”. Our genome is a blueprint for many potential biological selves.
Ex: Twin studies; chronic social isolation study (both regarding expression of genes).
Diathesis-Stress Model
Some individuals have a predisposition (diathesis) that makes them more vulnerable to negative environmental influences (e.g., stress).
Differential Susceptibility Model
Some individuals are more sensitive to both negative and positive environmental influences.
Ex: Maternal care as a newborn vs. child outcomes.
Epigenetic change
A type of change to structure of DNA that affects gene expression without altering the underlying DNA sequence. I.e. Factors that affect whether a gene is “read” or not. Is reversible, but can have long lasting effects.
Ex: Rat moms with high or low LG.
Methylation
Process by which a methyl group attaches to some of the parts in DNA. Influences the production of a gene’s specific protein; mehtylated genes are generally “shut off”.
Behavioural genetics
Study of strength of genetic influences on a behaviour/trait/disorder.
Heritability
How much of variation in phenotype across people can be attributed to
variation in genotype. Applies to populations, not individuals. Calculated as a proportion ranging from 0 to 1
- 0: Genes do not contribute to how people differ
- 1: Only genetic factors are responsible for differences.
**Typical range of a trait is between .3 and .6 (30% - 60%)
Ex: With identical twins, one can examine variation in genes while holding environment constant, or vice-versa.
Identical/monozygotic twins
Share 100% of their DNA. Develop from the division of a single fertilized egg.
Fraternal/dizygotic twins
Share 50% of their DNA. Develop from two seperate eggs.
Evolution
Change in species over time; descent with modification from a common ancestor.
Artificial selection
Human-controlled selective breeding.
Natural selection
Process through which certain traits become more or less common in a population over time due to pressures of the environment.
Three key components:
1. Variation
2. Heredity
3. Differential fitness
Variation
Within a population of organisms, there is variation in traits or characteristics.
Heredity
Some of this variation is passed down from parents to offspring (we know know this is through genetic inheritance). Either through the reshuffling of genes during sexual reproduction on mutations.
Mutations
Errors during DNA replication.
Differential fitness
Not all individuals in a population survive and reproduce equally.
Adaptations
Favourable traits better suited to the environment that increase chances of survival & reproduction. These favourable traits gradually accumulate over generations.
Fitness
Interaction between characteristics & prevailing environment.
Functionalist approach in psychology (Functionalism)
Explains behavioural / mental / emotional / physiological processes by their utility.
Ex: Why do we help others? Why do men tend to be more aggressive than women?
Distal explanations of behaviour
What role did behaviour play in survival and reproduction over evolutionary time?
Ex: Male songbirds sing in the spring to attract females & warn other males to stay away.
Proximate explanations of behaviour
Immediate triggers of the behaviour.
Ex: Increased daylight in the spring triggers testosterone production which acts on brain regions responsible for singing.
Genes
The basic physical and functional units of heredity; made up of DNA.
If you assume there has been an adaptation you should…
See some evidence of univerality around the world, across different cultures, people.
Neuroscience
The study of how nerves and cells send and recieve information from the brain, body and spinal cord.
Neurodiversity
The appreciation of the inherent differences among individuals in how their brains function.
Genotype
The genetic makeup of an organism composed of the organism’s complete set of genes.
Allele
A variant form of a gene; humans have two alleles per gene, one inherited from each parent. Alleles influence a phenotype by having a strong (dominant) or weak (recessive) influence.
Gene expression
The turning on and off of genes in a particular cell to determine how that cell functions.
Epigenics
The study of how the interactions between your genes and the environment regulate your gene expression through chromosomal modifications and chemical modification of DNA bases.
Behavioural genetics
The study of how genetic factors influence trait variation (a difference in characteristics) between individuals, whether that trait is visible (ex: hieght) or more abstract, but still measurable (ex: emotional instability).
Heritability
An indication of how much variation in phenotype across people is due to differences in genotype.
Chromosome
A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
Limitations to twin studies
- Equal environment assumption in MZ vs DZ twin studies:
But MZ twins may be treated more similarly -> inflated heritability estimates. - Selective placement in MZ twin adoption studies leads to more similar environments.
- Complex gene x environment interactions.
MZ twins may create more similar environments.
Environmental influences on gene expression, epigenetic processes, etc.
The need to belong and the reason for why it emerged
Human beings have a fundamental need to form and maintain at least a minimum quantity of lasting, positive, and significant interpersonal relationships.
- Tendency to affiliate with others (and avoid exclusion) is an adaptation.
- Throughout our evolutionary history, group living served as multi-purpose survival tool:
Help hunting large game & foraging;
Sharing food;
Defensive vigilance and greater strength against predators and hostile outgroups;
Help caring for offspring;
Access to mates.
