Gene-Environment interplay Flashcards
What are the 3 main types of Gene-environment correlation (rGE)?
- Passive
- Active
- Evocative
We measure rGE using a range of designs
Name 3?
- Twin studies
- Adoption studies
- Molecular genetic studies
Explain HOW passive rGe can be detected?
and what association does it refer to?
- can be detected by comparing correlations between family environment and children’s traits in adoptive and non-adoptive families
- refers to association between genotypes a child inherits from their parents and the family environment
- can only occur between individuals who share both the family environment and genetic material
Passive rGE is implied if the correlation between family environment and the child’s trait is greater in non-adoptive than adoptive families.
True or False?
TRUE
The adoption design is not able to assess what 2 things?
- evocative rGE (an association between genetically influenced behaviour and the way people react)
- active rGE (when individuals select, create and modify their environmental experiences based on genetic dispositions)
Evidence was found for evocative gene-environment correlation for antisocial behaviour in adolescence.
true or false?
TRUE
What is the difference between twin studies and GCTA ?
Twin studies • Family-based • Depend on special samples, i.e. twins • Involve a few hundreds of pairs of participants. • Require no DNA
GCTA • Population-based • Can use any sample of unrelated individuals • Can involve thousands of people • Requires DNA - genetic influences measured using SNPS • Needs GWA data
Gene-environment correlation (rGE) is of interest for several reasons
name 3?
- It can bias heritability estimates of traits associated with the environment in question.
- To interpret heritability estimates, it is important to understand how rGE can affect them.
- rGE can have implications for our understanding of relationships between environmental variables and traits.
The most common way to estimate heritability is comparing correlations between MZ twins with that between DZ twins.
true or false?
TRUE
active or evocative gene-environment correlation occurs leading to?
- increased genetic resemblance between MZ twins will lead them to seek similar environments, making MZ twins more alike than DZ twins
- increases A, the heritability estimate
Passive rGE leads to?
all children biologically related to their parent inherit an environment that correlates with their genome
true for all twins, MZ or DZ, who will become more alike
increases resemblance of DZ twins relative to MZ twins
increases C, shared environment estimate
If passive rGE is more important during infancy and childhood, and active rGE becomes more important as children develop, what would you expect to happen?
Heritability to increase over development, with the relative importance of the shared environment decreasing
If passive rGE is more important during infancy and childhood, and active rGE becomes more important as children develop, what would you expect to happen?
Heritability to increase over development, with the relative importance of the shared environment decreasing
Passive rGE makes MZ and DZ twins more alike, so increases estimates of shared environment.
true or false?
TRUE
Active rGE is driven by the child’s genes so makes MZ twins more alike than DZ twins, increasing heritability.
True or False?
TRUE
Many twin studies support the notion that different forms of rGE are important at different stages of development.
True or False?
TRUE
In childhood, large C combined with small A suggests that MZ and DZ twin pairs were equally similar.
This aligns with the notion of passive rGE being important for childhood depression
True or False?
TRUE
passive rGE is important in?
Childhood
active rGE becomes more important when?
In adolescence
As children age, they may seek out environments that suit their genetically influenced ‘g’.
True or false?
TRUE
It is not possible to use twin studies to investigate correlations between environmental variables and behavioural traits.
True or false?
FALSE
It is possible to use twin studies to investigate correlations between environmental variables and behavioural traits.
What is maternal negativity?
- negative maternal behaviours directed towards a child
- is associated with adolescent antisocial behaviour
- often considered an environmental risk factor - external to the individual, predicts a particular outcome
Putative environmental variables are often heritable. As such, genes associated with the environment might?
Overlap
Maternal negativity might correlate with adolescent antisocial behaviours because the same genes are involved.
True or false?
TRUE
Genome-wide Complex Trait Analysis estimates what?
Heritability using unrelated singletons
For some environmental variables, it is not possible to calculate heritability using the twin method.
Why is this so?
Some variables will always be the same for twin pairs regardless of zygosity
Because GCTA does not use related individuals, it is possible to calculate the heritability of such environmental variables.
True or false?
TRUE
It has been shown that family socioeconomic status is heritable, and genes associated with socioeconomic status also associate with what?
children’s intelligence
educational achievement
Many putative environmental variables we have discussed are in fact parental variables.
The fact that parent and child are related to one another means that rGE is always possible for any association between parent and child.
True or false?
TRUE
Parents and children share DNA, so any parental risk factor could associate with offspring outcomes because?
parenting directly influences child development
and/or
parents and children share genes associated with both parenting and child outcome
If the child’s genes correlate with the parenting, it is difficult to identify whether parenting is a risk factor.
True or false?
TRUE
Are there designs that allow us to disentangle genetic transmission from the possibility of environmental effect?
YES
A research design for studying associations between parent and offspring. It involves using samples of twin pairs where each twin has a child.
What can this study design be used to study? 6 things
- intergenerational transmission of mental health problems
- effects of parenting style on child development
- effects of home environment
- effects of in-utero environment
- impact of adolescent motherhood
- effects of family composition
What are avuncular correlations?
aunt/uncle and niece/nephew correlations in mz and dz twins
Cousins share how much of their genetic variance?
12 and 1/2 of their genetic variance
Let’s imagine there are two brothers. They will share on average what percentage of segregating genes?
50 %
Now, imagine they each have a child. They will pass on what % of DNA on to their child?
50%
To calculate the genetic relatedness between brother 2 and child 1, the avuncular association, we can do what?
multiply the paths that connect them
the parent-child path and the brother-brother path– that is, 0.50 times 0.50 equals 0.25
So uncle and niece or nephew share 25% of their segregating genes.
What do path tracing rules allow?
allow us to calculate the relatedness between cousins
in this case, 0.5 by 0.5 by 0.5. This gives us 0.125.
So cousins share 12 and 1/2% of their segregating genes on average
However, things are slightly different when it comes to monozygotic twins. When monozygotic twins have children, those children are as genetically related to their aunt or their uncle as they are to their own parent
True or False?
TRUE
In effect, they receive half of their genes from both their parent and his or her co-twin, but they receive their rearing environment from the parent only
True or false?
TRUE
So if parent-child correlations are larger than avuncular correlations, then this implies a role for?
a rearing environment in explaining intergenerational associations
Monozygotic avuncular correlations involve a genetic association of?
0.5
Dizygotic avuncular correlations involve a genetic association of?
0.25
the association between parental depression and offspring internalizing is not attributable to genetic transmission, and instead involves exposure.
true or false?
TRUE
Topic 3: Investigating gene-environment interaction
Define gene-environment interaction?
Interactions refers to the differential effect of one variable at different levels of another variable.
When do these interactions occur?
occur when environmental risks change as a function of genetic risk - or genetic risks are only expressed in certain environments.
Genetic effects might only show up in certain environments.
An environmental influence might only have an impact when it’s combined with specific genetic risk.
TRUE OR FALSE?
TRUE
Do genetic and environmental influences combine in an additive fashion?
NO
What is Phenylketonuria (PKU)?
Phenylketonuria (PKU) is a rare genetic disorder that leaves individuals unable to metabolise phenylalanine.
Individuals must have two copies of the PKU allele to be affected.
Carriers of the PKU allele have a 1⁄4 chance of having an affected child.
PKU can lead to serious intellectual disability as it causes phenylalanine to build up in the blood and brain.
The effects of the PKU allele can be ameliorated by what?
changing the environment – an example of GxE.
Why does this occur?
This is because the genetic effect only occurs in the presence of the amino acid and its negative effects only occur in the presence of the PKU allele.
If PKU is diagnosed at birth what can be done?
the affected individuals can be put on a special low- protein diet which reduces the levels of phenylalanine in the body and prevents brain damage.
What are the symptoms of PKU?
PKU doesn’t usually cause any symptoms if treatment is started early.
However, if not treated early it may lead to abnormal brain development which in return would cause cognitive impairment
The exact implications of ignoring gene environment interactions depends on the type of environmental influence the genetic factors interact with.
AxC= ?
A
AxE=
E
The simplest way to look at whether heritability changes as a function of environment is?
to see whether A, C and E are different in different environments.
Twin research into GxE typically uses a structural equation model that allows the environmental moderator to have a main effect on the trait as well as a moderating effect on any or all of the residual A, C, E components of the trait.
True or False?
TRUE
Name 5 continuous variables?
Age
Socioeconomic status
Regional alcohol sales
Parental warmth
Family wellbeing
Do genetic influences on depression change as a consequence of the environment?
Yes, there are significant GxE with depressive symptoms and family conflict.
Molecular genetic approaches and GxE
What are the 2 approaches?
Candidate gene studies - focus on a single genetic variant
Genome wide-approach - information from the whole genome
