GENETICS + EVOLUTIONARY FOUNDATIONS OF BEHAVIOUR

genome

complete set of genetic material in an organism

DNA

molecule that carries genetic info, organized + packaged within chromosomes

gene

segment of DNA that codes for a particular protein

allele

version of a gene

genotype

2 alleles that code for a trait

phenotype

observable characteristics of an individual, produced by interaction of genotype + environment

recessive alleles

determine phenotype only when an individual is homozygous for a gene

dominant alleles

determine phenotype regardless

behavioural genetics

establishes degree of heritability for a given trait

evolutionary psychology

examines why certain genetically encoded behaviours + traits emerged

gene knockout

removal or deactivation of a gene

gene knockdown

make gene less active

diathesis-stress model

some individuals have a predisposition (diathesis) that makes them more vulnerable to negative environmental influence

differential susceptibility model

some individuals are more sensitive to both negative and positive experiences

phenotypes

product of genotype + environmental influence

gene expression

environmental factors affect which genes are turned ‘on’ and ‘off’

epigenetic change

a type of change to structure of DNA that affects gene expression without alternating underlying DNA sequence

methylation

process by which a methyl group attaches to some of the parts in DNA (influences whether the gene will produce the protein)

behavioural genetics

study of strength of genetic influences on a behaviour/trait

heritability

how much of phenotypical variation across people can be attributed to genotypical variation (proportion ranging from 0 to 1)

evolution

change in species over time

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 from the environment

3 key components of evolution by natural selection

variation, heredity, differential fitness

variation

variation in traits/characteristics are present in populations (typically due to reshuffling of genes during sexual production or mutations)

mutations

errors during DNA replication

heredity

some of this variations is passed down from parents to offspring

differential fitness

not all individuals in a population survive and reproduce equally

adaptation

favourable traits better suited to the environment, greater chances of survival and reproduction

fitness

interactions between characteristics and environment

distal explanations of behaviour

the role behaviour plays in survival and reproduction over evolutionary time (eg. male birds sing in spring to attract females)

functionalist approach

explains behavioural/mental/emotional processes by their utility

proximate explanations of behaviour

immediate triggers of behaviour (eg. more daylight in spring triggers testosterone production which acts on brain regions responsible for singing)

limits of evolutionary explanations for behaviour

difficulty testing hypothesis, common behaviour ≠ adaptive behaviour

chromosome

threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell

homozygous genotype

having two identical versions of the same gene (ex. both eye colour genes code for brown eyes)

hetereozygous genotype

having two different versions of the same gene (ex. mother’s genes code for brown and father’s genes code for blue)

how do genes and environments interact

some organisms change trains in response to environmental conditions, gene expression, epigenetics, developmental plasticity

candidate gene study

compare individuals with the candidate gene with individuals without on a given trait or disorder

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

gene expression example factors

stress, chemical exposure, hormone signals, temperature of the environemnt

examples of epigenetic change

• high-LG rats spend a lot of time licking and grooming their offspring, when cross-fostering pups of low-LG moms, adoptive high-LG moms give their foster pups their traits and those pups become high-LG moms, proving behavioural transmission of differences despite genes

• biologically, this is bc exposure to high-LG mothering demethylation → greater expression of glucocorticoid receptors in hippocampus → more negative feedback → lower circulating glucocorticoid levels

how twin studies help study heritability

can examine variation in environment, while holding genetics stable or examine variation in genes while holding environment relatively stable

need to belong

refers to the fundamental human need to form and maintain at least a minimum of lasting, positive, and significant interpersonal relationships, evolved via group living in evolutionary history

identical/monozygotic twins

100% shared DNA

fraternal/dizygotic twins

50% shared DNA