lecture 7 part 1

Question 1

Heritability

Answer 1

the proportion of this total variation between individuals in a given population due to genetic variation

Question 2

The question of whether a trait is heritable is a about

Answer 2

the role that differences in genes play in the phenotypic differences between
individuals or groups within a population

Question 3

Heritability estimates for IQ are around

Answer 3

0.5, Some estimates as high as 0.8

Question 4

what are the three major considerations of heredibility

Answer 4

1. A heritability coefficient is always specific to a
   particular population at a particular time
2. Heritability is a measure of variation
3. A high heritability coefficient does not mean that a trait “is genetic”

Question 5

1. A heritability coefficient is always specific to a
   particular population at a particular time

Answer 5

the heritability of weight is approximately 0.6 in North America. Would this coefficient be expected to change if we measured it 1000 years ago in Medieval
England?

Question 6

2. Heritability is a measure of variation

Answer 6

For some attributes there may be no person-to-person variation

Question 7

3. A high heritability coefficient does not mean that a trait “is genetic”

Answer 7

If the heritability of weight was 1 would this mean that one’s weight is 100% determined by genes? No, Genes cannot be understood outside the context of the
environment with which they interact.

Question 8

2nd consideration of heretibility example

Answer 8

tried to determine the heritability of
“having a heart” found that h2 was equal to 0. What
does that mean?

heart development is strongly influenced by genes and there is no variation across the sample :
everyone has a heart so the coefficient is 0

Question 9

3rd consideration of hereditability explanation

Answer 9

heritability coefficient of 1 does mean that trait differences
between individuals within a population at a time are due to genetic factors. if a certain portion of the trait is invariant across the population, heritability does not account for genetic influences on the portion of the trait that does not vary. – Also, if you change the population/time, you will change the
heritability coefficient

Question 10

3 laws of the genetics of complex traits

Answer 10

• Intelligence has some genetic basis
• Intelligence is not
  100% heritable
• Intelligence may be caused by many genes of small effect

Question 11

1. Intelligence has some genetic basis

Answer 11

• Rett syndrome
• William Syndrome
• Fragile X syndrome

Question 12

rett syndrome

Answer 12

rare genetic neurological disorder that mainly affects girls.

leads to severe cognitive and physical impairments. often experience loss of purposeful hand skills, impaired motor functions, repetitive movements (such as hand-wringing), and problems with communication and social interactions

Question 13

willimas syndrome

Answer 13

genetic condition characterized by developmental delays, learning disabilities, and distinct facial features. They may face challenges in spatial tasks and have a higher likelihood of heart problems

Question 14

fragile x syndrome

Answer 14

a genetic disorder more common in males that causes intellectual disability, behavioural challenges, and various physical characteristics. often have social and communication difficulties and repetitive behaviours, and may exhibit symptoms of autism spectrum disorder, hyperactivity and sensory sensitivities

Question 15

2. Intelligence is not 100% heritable

Answer 15

• All traits show some
  environmental influence
• also Interplay
  between genes and
  environment

IQ = Genes + Environment
+ Interaction + error

Question 16

Gene x Environment interaction

Answer 16

An interaction effect is not the same as a correlation

Interaction effects quantify how genetic characteristics can change the influence of an environmental variable

Question 17

gene x environment interaction example

Answer 17

researchers were able to identify a gene that was associated with severe violent behaviour, but only for individuals who had been victims of abuse during childhood.

Individuals who had not been victimized, but who carried the
gene were less likely to commit violence

Question 18

3. Intelligence appears to be caused by many genes of small effect
   (polygenic model)

Answer 18

Genome-wide association (GWA) studies

Question 19

• Benyamin et al 2014

Answer 19

• 18 000 children
• No genome-wide significant associations of IQ with 1 gene
• Largest effect sizes = 0.2% of the variance of intelligence scores

Question 20

Desrivieres et al 2014

Answer 20

• 1500 children
• Largest effect sizes = 0.5% of the variance of intelligence scores
• Genes can also interact (i.e., the expression of one gene might depend
  on the presence of another gene)

Question 21

human genome project allows

Answer 21

estimates of genetic influence on
complex traits using genome-wide genotypes
in large samples of unrelated individuals

Question 22

what is the human genome project limited to

Answer 22

additive genetic variance

Question 23

Heritability of intelligence increases from
infancy to adulthood.

Answer 23

Small genetic differences are magnified as children select, modify and create environments
correlated with their genetic propensities (active model of selected environments)

Question 24

simplified of first of the five main findings

Answer 24

Proximal vs distal effect of genes

Question 25

The same genes are
responsible for the
heritabilities of these tests.

Answer 25

These tests seem to tap into different cognitive processes….
But still, these sub-tests would tap into
“similar” genes (Genetic correlations of 0.6)

Question 26

Assortative mating is
greater for
intelligence than
many other traits

Answer 26

spouse correlations for intelligence (~0.40)
* spouse correlations for height
and weight (~0.20)

Question 27

intelligence is
normally distributed

Answer 27

There is a positive end of high performance as
well as a problematic end of intellectual
disability

Question 28

The same genes underlie variations
in intelligence, education and SES”

Answer 28

cant really know what is causing
what but it is in line with some of the
data from 2 weeks ago…

Question 29

prenatal effects

Answer 29

borth weight, smoking/ alcohol use, and nutrition

Question 30

nutrition mixed results

Answer 30

Dutch famine study showed little long term effect of famine.

A large meta analysis suggested that all prenatal effects accounted for very little variation beyond maternal education

Question 31

post natal environment

Answer 31

nutrition, general health, pollutants, and education

Question 32

nutrition post natal

Answer 32

Sometimes post natal nutrition has effects, or not.

When malnutrition is severe it most certainly does.

Probably not a big factor on midrange IQs in the west.

Question 33

general health postnatal

Answer 33

High IQ is related to having better health

Question 34

pollutants postnatal

Answer 34

Has a demonstrable effect on IQ at high levels

`Low levels of pollution appear to have either very small or no effect

Question 35

If lead levels in the bloodstream reach 25 mg per 100 mL there will be

Answer 35

deleterious effects on IQ- level of lead exposure rare and associated with poverty

Question 36

education postnatal

Answer 36

Has meaningful effects on IQ and Effect on other cognitive test