Genes and the environment

Question 1

what did Mendel find in his pea breeding experiment

Answer 1

• First generation - all yellow
  
  • Second generation - one green and three yellow

Question 2

define homozygous

Answer 2

two copies of same allele

Question 3

define heterozygous

Answer 3

one copy of two different alleles

Question 4

define dominant

Answer 4

always expressed in phenotype if present in genotype

Question 5

what did Mendel find in the two gene case

Answer 5

independent segregation - different genes on different chromosomes that are independent of one another

Question 6

define recessive

Answer 6

only expressed in phenotype if both present

Question 7

What does the Hardy Weinberg theorem propose

Answer 7

Genotypes always appear in the frequency p2, 2pq and q2 (where p is the frequency of one allele and q is the other)= 1

Question 8

what is Hardy Weinberg theorem dependent on

Answer 8

an infinitely large population and no natural selection

Question 9

what is genetic drift

Answer 9

Because populations are finite, allele frequencies do in fact change (a little) by chance from generation to generation
Neutral alleles change in frequency over time even without natural selection

Question 10

what is genetic drift useful for

Answer 10

tracking evolutionary descent

Question 11

why is it difficult to establish which alleles are related

Answer 11

finding gene with minimal environmental input is difficult

Question 12

what do phenotypic correlations have

Answer 12

a genetic component G plus a shared environment component C

Question 13

what are used to show phenotypic correlations

Answer 13

twin studies show

Question 14

what do twin studies show about phenotypic variability

Answer 14

The higher the heritability of the trait, the bigger the proportion of variation in phenotype that is explained by the genotype, then the bigger the difference between MZ and DZ correlations

Question 15

what are the different components of variation

Answer 15

G or A: Variation due to genes
C: Variation due to shared environment
E: Variation due to unique or non-shared environment

Question 16

what is heritability

Answer 16

what proportion of variation in the phenotype can be explained by variation in the genotype

Question 17

Falconer’s estimate of heritability

Answer 17

corrMZ = G + C (100% shared genetics)
corrDZ = ½ G + C (50% shared genetics)
- corrMZ – corrDZ= ½ G
G = 2 * (corrMZ – corrDZ)

Question 18

meaning of number in heritability

Answer 18

Number between 0 and 1 - reflects proportion of variation in that population due to variation in genotype

Question 19

example of how heritability is not fixed

Answer 19

• Impoverished families - 60% of the variance in IQ is accounted for by the environment, and the contribution of genes is close to zero
  Affluent families - almost exactly the reverse

Question 20

Can we discover how genes and environment influence behaviour

Answer 20

in principle; it’s about mechanisms
However difficult to disentangle the genetic and environmental causes of behaviour

Question 21

what is the cake analogy

Answer 21

-Individual ingredients of a cake cannot be distinguished in the final product, but we know they exist
-Similarly, the influences of genes and environment on behaviour are not always easy to discover, but they must exist

Question 22

what does interaction mean

Answer 22

Genetic influence varies with the environment

Question 23

what is the MAOA gene

Answer 23

on X chromosome -makes enzyme that metabolises neurotransmitters to recycle - genetic deficiencies

Question 24

what results in flawed MAOA production

Answer 24

Faulty gene – no MAOA
Polymorphisms – variation in MAOA production

Question 25

What did Caspi et al find about MAOA gene on maltreated children

Answer 25

• There is an interaction between genetic influence and environment - those with severe maltreatment and low MAOA highest levels of antisocial behaviour
  
  • Environment has impact initially but more severe when paired with genetic influence
    Genetic influence alone had little link

Question 26

What did Newman find in Rhesus monkeys

Answer 26

Those with worse (peer) upbreeding showed lower aggression and those with better upbringing (mother) showed higher aggression and impact of low MAOA activity

Question 27

what do these studies tell us

Answer 27

There is evidence that genes and your childhood experiences can impact upon your behaviour (aggression/violence)

Question 28

confounding factors of these studies

Answer 28

Methodological differences
Subject differences - different species - different expectations for aggression e.g. important for monkeys

Question 29

Conclusions of this research

Answer 29

Research can be conducted trying to tease apart the effects of genes and the environment on behaviour, but it often requires many studies in order to piece together what is happening.

Question 30

what does evolution suggest about impulsivity

Answer 30

suggest impulsivity should be sensitive to the current state of the organism

Question 31

What did John Locke suggest

Answer 31

blank slate - everything is learnt from experience

Question 32

what do behaviourists do

Answer 32

emphasis role of the environment

Question 33

what do psychologists believe about blank slate

Answer 33

rejected - believe both nature and nurture play a role

Question 34

Ockham’s Razor

Answer 34

All things being equal, the simplest solution tends to be the best one