Flashcards in Genetics and evolution of personality traits Deck (75)
What are the main properties of traits?
• normally distributed (between individuals)
• heritable (if fixed via natural selection as a universal, heritability should be 0)
• intra-individual stability (does trait expression differ day to day?)
• inter-individual difference (universal = minimal variability, but people differ)
• inter-correlated, e.g. extraversion and openness to new experiences.
What are the two main Darwinian mechanisms driving evolution?
Natural and sexual selection.
What does natural selection involve for traits?
• variation - population property, discretely and continuously varying traits
• differential reproduction of resulting phenotype
What two factors determine fitness?
Survivorship and fecundity (no. of offspring).
What are the three causes of genetic variation?
• sexual recombination
• gene flow (moving to a new population)
What are the two kinds of sexual selection?
• inter-sexual (mate selection)
• intra-sexual (competition)
What are the different types of genetic mutation which can occur?
• copy number variation (CNV) - repetition of segments due to replication/duplication errors.
• single nucleotide polymorphism (SNP) - replication errors via base pair substitution
• translocations or inversions - re-arrangements of large chromosomal regions
The speed at which new mutations enter the functional genome.
What is the mutation-rate in humans?
1.67 per individual per generation, about 1 in 5 born without a new mutation.
What is the mutation load?
Mildly harmful recessive mutations - each human has about 500.
What are the three modes of selection?
Directional, stabilising, and disruptive.
What does directional selection involve?
Individuals low on the trait value scale have low fitness and are selected against, causing the whole normal distribution curve to shift to the right.
What are some examples of directional selection?
Evolution of IQ and Darwin's Finches' bills.
What does stabilising selection involve?
Individuals who are low and high on the trait value scale have low fitness and are selected against, causing the variation and sd of the normal curve to decrease.
What environments is stabilising selection common in, and give an example.
Stable environments, sickle cell anaemia - 2 recessive or two dominant not adaptive, one recessive one dominant increases survivorship.
What does disruptive selection involve?
Individuals in the centre of the trait value scale are selected against, causing a dip around the mean of the curve.
When is disruptive selection seen?
The proportion of total phenotypic variation in the population that is due to genetic variation (h^2).
What have psychological tests found regarding heritability?
Heritability increases with aggregated measures, reliable measures, and where there is variation.
The construction and application of psychological tests; mental measurement.
What genetic variance is and is not transmitted from one generation to the next?
Is: additive effects
Isn't: dominance and epistasis.
The interaction of alleles at the same locus of a chromosome.
The interaction of alleles at different loci of a chromosome.
What should natural selection favour?
A single best adapted phenotype for optimal species fitness, e.g. eyes.
What mechanisms were suggested by Penke, Denissen and Miller (2007) for the evolution of personality?
Selective neutrality, mutation-selection, and balancing-selection.
How does selective neutrality work?
• Fitness neutral mutations build up and lead to increased genetic variation in the trait.
• only affected by genetic drift, as natural selection is blind to it.
• traits don't affect fitness
• genetic variation would be additive, however most traits show non-additive effects.
How does mutation-selection-balance work?
• natural selection balances the effects of mutation in terms of trait variance
• additive variation increases with trait fitness, but this is most selected genetic component.
• more susceptible to 'inbreeding depression' and 'outbreeding elevation' (e.g. IQ), which is not the case for personality.
• traits should be sexually attractive and show assortative mating, which is not the case for personality.
The existence of more than one type of allele at a chromosomal locus which determines phenotype.
How does balancing-selection work?
• extremes of a trait are favoured to the same degree by different environmental contingencies.
• overdominance - individuals with heterozygous pairs are fitter than homozygous pairs.
• antagonistic pleiotropy - polymorphism has a positive effect on one trait and a negative effect on another.
• environmental heterogeneity - fitness varies across time and space and is on average neutral across contexts.
• frequency-dependent selection:
- positive = favours traits with high frequency (runaway selection)
- negative = favours traits with a low frequency