Developmental genetics

Question 1

Plomin et al (1997) (2016) (2023)

Answer 1

Genetic differences are amplified and grow across development as individuals influence, select and modify environments correlated with their genotype.

There are three types of gene-environment correlation:
Active - when an individuals genetically linked traits influence the environments they choose for themselves, more likely important beyond childhood once individuals have greater opportunity for active selection of environments
Evocative - when an individuals genetically influenced characteristics evoke responses from their environment, can occur across the lifespan, likely to be more important than active in early development as young children have limited control over direct selection of modification of their environments
Passive - parental genes transmitted to the child are correlated with the caregiving environment, hard to know if associations between children’s genetics and their environments are due to genetic transmission, the caregiving environment or both, particularly important during childhood if individuals are living with biological parents

Discovery from GWAS that the biggest SNP effect sizes were tiny. On their own, single variants tend to have small effects on complex traits and limited predictive power so these can be combined into Polygenetic Scores (PGS) for prediction.

Question 2

McGue et al (1993)

Answer 2

Behavioural genetics of cognitive ability: A life-span perspective. Twin studies find increasing heritability of IQ over life. Likely due to genetic amplification through gene-environment correlation.

Question 3

Wang et al (2022)

Answer 3

PGS shows poor generalisability in non-European populations. Efforts are underway to increase their accuracy across diverse groups.

Question 4

Austerberry and Fearon (2021)

Answer 4

Gene-environment interaction. Strength of genetic influence varies as a function of the environment. There is fairly limited evidence of this in human studies.

Question 5

Baker and Kedler (2007)

Answer 5

Systematic review of studies examining the heritability of 35 ostensibly environmental measures found a weighted heritability of 27% across each.

Question 6

Krapohl et al (2017)

Answer 6

Covariation between polygenetic variation and environmental exposures such as household income, breastfeeding, and parental age, behaviour and education.

Question 7

Connolly et al (2015)

Answer 7

Multivariate genetic analysis found that common genetic factors underpinned the phenotypic correlation between antisocial behaviour and deviant peer associations in adolescence. Evidence of active gene-environment correlation.

Question 8

Tarantino et al (2014)

Answer 8

Substantial genetic contributions to deviant peer affiliation across adolescence (15-21) which suggests heritable traits contributed to a young persons tendency to seek out or perhaps be sought out by deviant peers. Evidence of active gene-environment correlation.

Question 9

Ge et al (1996)

Answer 9

Children aged 12-18 years whose birth mothers showed high levels of externalizing problems received more negative and harsh parenting from their adoptive parents relative to those children whose birth mothers did not have externalizing problems. Evidence of evocative gene-environment correlation.

Question 10

Marceau et all (2013)

Answer 10

Evidence from twin, sibling and extended children-of-twins designs suggesting that evocative gene-environment correlation may explain the correlation between adolescents externalizing problems and parental negativity.

Question 11

Leve et al (2019)

Answer 11

One of the few studies to have comprehensively examined evocative gene-environment correlation in early childhood is EGDS adoption study.

Question 12

Klahr et al (2017)

Answer 12

EGDS has found evidence of evocative effects on parenting in infancy and toddlerhood of genetic factors linked to internalising and externalising psychopathology, low social motivation, and attention-deficit hyperactivity disorder.

Question 13

Wertz et al (2020)

Answer 13

Children’s polygenetic scores associated with the home environment and maternal parenting even after controlling for maternal polygenetic scores. Genomic evidence of evocative gene-environment correlation.

Question 14

Agnew-Blais (2022)

Answer 14

Children’s ADHD polygenetic scores associated with household chaos over and above maternal polygenetic scores. genomic evidence of evocative gene-environment correlation.

Question 15

Rice et al (2013)

Answer 15

In a sample of children conceived via assisted reproduction, Evidence of passive gene-environment correlation when parent-child associations in depressive symptoms were compared within genetically related and non-genetically related families.

Question 16

Koellinger and Harden (2018)

Answer 16

Fast growing literature on ‘genetic nurture’ discovery that the parts of the parental genotype not transmitted to offspring predict offspring educational outcomes. Implication that the same is true of the transmitted genes, their associations with children’s outcomes are at least partly confounded by correlated environments and are not solely attributed to direct genetic transmission. Evidence of passive gene-environment correlation.

Question 17

Cheesman et al (2020)

Answer 17

Polygenetic scores are twice as predictive of educational outcomes in nonadopted individuals compared with adoptees, suggesting that family environments play an important role in the manifestation of genetic effects on education. Evidence of passive gene-environment correlation.