Nature and nurture interplay

Question 1

In the UK sample of 12-year old twins, the correlation for language ability for MZ twins was 0.67 and for DZ twins was 0.43. What are the estimated genetic and environmental effects on this trait?

Answer 1

G=48%
E=52%

MZ- DZ x2 0.24 x 2 = 0.48 (48%)

Question 2

Do Genes and Environment contribute independently to a specific trait?

Answer 2

Genes and environment interplay, they co-act therefore they do not act individually

Increasingly, studies are focusing on how the environment moderates and mediates genetic risk

Question 3

What is the type of Gene-Environment interplay for:
1. Epigenetics
2. Gene-Environment Correlation
3. Gene-Environment Interaction

Answer 3

1- environment influences genetic (E → G)

2- genetic influences environment (G → E)

3- influence each other (G x E)

Question 4

Genetics:
1- Where is Genetic material (DNA) passed on from?
2- Human genome is built with ____?
3- How many genes are there in the human genome?
4- How much of the DNA sequence is the same for everybody and how much is variable?

Answer 4

1- passed on from parents to offspring (vertical genetic transfer)

2- 3 billion nucleotide base pairs (3,000,000,000)

3- There are 20-25,000 genes in the human genome

4- More than 99% of the DNA sequence is the same for everybody; ~ 1% of the DNA sequence is variable (the source of individual differences)

Question 5

What is gene expression?

Answer 5

Process by which the DNA sequence of a gene is converted into functional protein structures

Question 6

Gene Expression?
- name the sequence of events
- how does the process vary?

Answer 6

Gene will be used to encode RNA and the the RNA molecule will be used to produce protein.

This process varies across the life course

Question 7

Genetics compared to Epigenetics

Answer 7

Genetics (i.e., DNA sequence) determines what specific proteins are synthesized.

Epigenetics determines how much of the proteins is made, and where and when it is synthesized

Question 8

What is DNA Methylation?

Answer 8

Methyl groups attach to DNA compacting it and preventing its code from being read or made into proteins

Question 9

What are the factors that can influence epigenetic modulation

Answer 9

• Diet
• Psychological state
• Social interactions
• ALternative medicine
• Therapeutic drugs
• Microbiome
• Exercise
• Financial status
• Drugs of Abuse
• Toxic Chemicals
• Disease exposure
• Diurnal/ seasonal correlations

While some of these might be beneficial for health and behaviour, others might be harmful and interfere with the body and mind creating an imbalance, which might manifest as a disease or psychological disorder.

Beneficial influences listed are exercise, microbiome (beneficial intestinal bacteria) and alternative medicine whereas harmful influences include exposure to toxic chemicals and drugs of abuse.

Factors such as diet, seasonal changes, financial status, psychological state, social interactions, therapeutic drugs, and disease exposure might have beneficial or harmful effects depending on the specific nature of the influence.

The environment thus complements and shapes human health. With the help of extended research in the field, we might be able to steer these influences in a positive way.

Question 10

Maternal licking & offspring behaviour:
- who do high and low nurturing mothers raise?
- what does the nurturing behaviour of mothers shape?
- what does the epigenetic pattern that mom establishes do?

Answer 10

• High-nurturing mothers raise low anxious offspring
  Low-nurturing mothers raise high anxious offspring.
• The nurturing behaviour of a mother rat shapes her pups’ epigenomes: in offspring of low-nurturing mother (a), glucocorticoid receptor gene (Nr3c1) is switched off and leads to higher level of stress and anxiety.
• The epigenetic pattern that mom establishes tends to stay put, even after the pups become adults.

Question 11

Maternal licking & offspring behaviour
- what is GR responsible for?
- what is found between low licking and grooming and high licking and grooming

Answer 11

GR is responsible for mood regulation

Low licking and grooming:
Decreased GR expression
High corticosterone levels
High anxiety
Low licking and grooming

High licking and grooming:
Increased GR expression
Low corticosterone levels
Low anxiety
High licking and grooming

Question 12

Maternal care and epigenetics:
‘Lick your rats’- what did they show?

Answer 12

They showed it can be reversed

Good mothering: a good rat mother licks and grooms her pups. She gives them extra space to suckle against her underside.

Bad mothering: a bad rat mother barely licks her pups and provides almost no tactile stimulation.

Question 13

Nature via Nurture

Answer 13

The environment is not independent of the person: humans select, modify and create environments in line with with their genetic propensities

Question 14

Gene-Environment Correlation (rGE)

Answer 14

When individuals with a genetic propensity for a trait are in environments, choose or create the environments, that support expression of the trait

Question 15

What are the three types of GE correlation

Answer 15

Passive:
Parental genes influence parental behaviours that play a role in determining the kind of rearing environment that they provide

Evocative:
Child genes influence child behaviours that play a role in evoking different types of responses in other people

Active:
Child genes influence child behaviours that play a role in determining how children shape and select their environments

Question 16

Three types of GE correlation linked with the source

Answer 16

Passive: parents and siblings
Evocative: anybody
Active: anybody or anything

Question 17

Passive GE correlation
Explanation and examples

Answer 17

Parental genes influence parental behaviours that play a role in determining the kind of rearing environment that they provide to their children

Examples:
- Parents of high IQ provide genes and enriched rearing environments
- Children with genetic vulnerability to antisocial behaviour is exposed to family maltreatment (because genetic factors parents have influence children antisocial behaviour but also influence the living environment)

Question 18

Evocative rGE
Explanation and examples

Answer 18

Genes influence people’s behaviours that play a role in evoking different types of responses in other people

Examples:
- Children with genetic risk for behavioural problems evoke a negative type of parenting or negative reaction from peers
- Children with positive personality (high extraversion) evoke more positive responses from parents/peers

Question 19

Evocative rGE:
Adopted children genetic status and adoptive parent’s negative control

Answer 19

A longitudinal adoption design provides a unique opportunity to investigate this issue in terms of genotype-environment correlations for behavioral problems. As part of the Colorado Adoption Project, adopted children were classified as being at genetic risk (N = 38) or not at genetic risk (N = 50) for antisocial behavior based on their biological mothers’ self-report history of antisocial behavior collected prior to the birth of the child. From age 7 through age 12, adoptive parents reported on the negative control, positive parenting, and inconsistent parenting they use in managing their child’s behaviour.

Repeated measures analysis of variance indicated that children at genetic risk were consistently more likely to receive negative parenting from their adoptive parents than children not at genetic risk, indicating an evocative genotype-environment correlation.

Question 20

Active rGE:
Explanation and examples

Answer 20

Genes influence people’s behaviours that play a role in determining how people shape and select their environments

“rich get richer” effect

Examples:
- Athletic individual seeks out athletic endeavours
- Antisocial person seeks out antisocial peers

Question 21

rGE across development:
- what changes/ increases through development
- two possible mechanisms?

Answer 21

The relative importance of the three kinds of rGE effects changes with development:
- The influence of the passive rGE declines from infancy to adolescence, whereas the importance of the active rGE increases over the same period

• The degree to which experience is influenced by individual’s genetic factors increases with development

Two possible mechanisms:
- new genes become important (genetic innovation)
- individuals select their own experiences (genetic amplification)

Question 22

Nature by Nurture:
Gene - Environment Interaction (GxE)

Answer 22

• Genetically influenced sensitivity to specific environment
• In this case, genetic influences on a trait depend on the environment eg. person may have genetic predisposition to anti social behaviour but only in this specific environment will their genetic propensities establish
• Specific environments and genetic susceptibilities to these environments predict a trait

Question 23

GxE: example
Child conduct problems as a function of genetic risk and physical maltreatment

Answer 23

Maltreatment places children at risk for psychiatric morbidity, especially conduct problems. However, not all maltreated children develop conduct problems. We tested whether the effect of physical maltreatment on risk for conduct problems was strongest among those who were at high genetic risk for these problems using data from the E-risk Study, a representative cohort of 1,116 5-year-old British twin pairs and their families. Children’s conduct problems were ascertained via parent and teacher interviews. Physical maltreatment was ascertained via parent report. Children’s genetic risk for conduct problems was estimated as a function of their co-twin’s conduct disorder status and the pair’s zygosity. The effect of maltreatment on risk for conduct problems was strongest among those at high genetic risk. The experience of maltreatment was associated with an increase of 2% in the probability of a conduct disorder diagnosis among children at low genetic risk for conduct disorder but an increase of 24% among children at high genetic risk. Prediction of behavioral pathology can attain greater accuracy if both pathogenic environments and genetic risk are ascertained. Certain genotypes may promote resistance to trauma. Physically maltreated children whose first-degree relatives engage in antisocial behavior warrant priority for therapeutic intervention.

The more genetic risk factors the child has for anti social behaviours, the more likely problem behaviours will manifest in environmental conditions

Question 24

Two models for GxE

Answer 24

1. Diathesis-Stress/ Dual Risk Model
   Combination between negative environmental factors and negative environment
2. Differential Susceptibility Model
   When we have genetic propensities for antisocial behaviour for example but depending on the environment its genetic propensities can manifest in the negative outcome, but in the very in reach positive environment the same genetic propensities can manifest into the positive outcome.

Question 25

Two models for GxE
What do the graphs look like?

Answer 25

1. Diathesis-Stress/ Dual Risk Model
   Vulnerable individual goes from negative to positive but when reaching resilient individual it doesn’t increase further
2. Differential Susceptibility Model
   Plastic/ malleable individual goes from negative, past fixed individual, to positive (constant line, no plateau)