Genes and behaviour

Question 1

what do genes produce?

Answer 1

proteins

Question 2

how can genes influence behav through proteins?

Answer 2

neurons

hormones

brains

muscles

Question 3

what do expressed behaviours depend on?

Answer 3

gene x env interactions

Question 4

what do genes influence?

Answer 4

mechanisms for learning

Question 5

what is a key feature of most living organisms?

Answer 5

behavioural flexibility

Question 6

where are genes located?

Answer 6

on chromosomes (DNA coiled around histones) located in the cell nucleus

Question 7

what does gene expression involve?

Answer 7

transcription

translation

Question 8

what are proteins?

Answer 8

large, complex molecules that do most of the work in cells

Question 9

examples of proteins

Answer 9

antibodies

enzymes

messengers - e.g. hormones

structural components - e.g. membrane channels, actin in muscles

transport/storage

Question 10

how much of the vertebrate genome codes for proteins

Answer 10

1.5%

Question 11

what is the relationship between amount of chromosomal DNA and organism’s complexity?

Answer 11

no consistent r’ship

Question 12

what amount of DNA do 2 humans share?

Answer 12

99.8%

Question 13

how much of their DNA do humans share with chimpanzees?

Answer 13

98%

Question 14

what % of DNA do humans share with mice?

Answer 14

92%

Question 15

genotype

Answer 15

the set of genes an individual possesses

Question 16

phenotype

Answer 16

the observable characteristics of an individual, influenced by genes and environment

Question 17

alleles

Answer 17

Individuals have one or two alleles (variants) of a gene, but multiple alleles can exist in the population

e.g. eye colour

Question 18

agouti gene

Answer 18

involved in coat pattern and shading of mammals

when upregulated, hair follicle melanocytes switch from making black to yellow pigment

Question 19

lethal alleles

Answer 19

lead to death of homozygous recessive offspring

Homozygous yellow-coated mice die as embryos

Question 20

polygenic inheritance

Answer 20

(multi-gene) inheritance of human skin colour

additive genetic variance

alleles A, B, Cdominant, dark pigmentation (more melanin)

alleles a, b, crecessive, light pigmentation (less melanin)

each parent produces eight different types of gametes

these combine with each other in 64 different ways

results in a total of seven skin colours

Question 21

challenges of behavioural genetic research - Sokolowski (2001)

Answer 21

difficulty in defining and quantifying behaviour

environmental influences on behaviour

within- and between-individual variation in behaviour

involvement of many genes

different genes function in different tissues at different times during the development of an organism

Question 22

burrow structure in Peromyscus mice

Answer 22

Deer mouse (P. maniculatus)

• lives in grassy/forest habitat
• builds burrows with short entrance tunnel and no escape tunnel

Oldfield mouse (P. polionotus)

• lives in open habitats (beaches, fields)
• builds burrows with long entrance tunnel and escape tunnel

Question 23

burrow structure in Peromyscus mice - Weber et al. (2013)

Answer 23

Captive-reared mice placed in sand-filled arena for first time
- builds species-typical burrow

F1 offspring of maniculatus × polionotus hybrid
- 100% escape tunnels

Backcrossed F1 × maniculatus
- ~50% escape tunnels

single, dominant locus controls building of escape tunnel

Question 24

foraging in fruit-fly larvae

Answer 24

Both behavioural types are wild-type phenotypes (70% rovers, 30% sitters in natural populations)

F1 offspring of female sitter x male rover
- essentially all same phenotype (rover)

F2 offspring of female F1 x male F1
- 3:1 phenotypic ratio

single gene influences expression of behaviour (but does not encode it)

Question 25

foraging in fruit-fly larvae - da Belle et al. (1989)

Answer 25

for gene encodes protein kinase G, which affects neuronal activity (short- and long-term memory)

sitters homozygous for recessive allele forS

rovers have at least one copy of dominant allele forR

Question 26

maternal behaviour in mice

Answer 26

fosB mutation in mice causes disruption of maternal behaviour: creating a nest, cleaning the pups, retrieving them to the nest, crouching over them for warmth and nursing

Single gene can determine phenotypic expression of complex behaviour

• fosB gene products widely expressed in brain, but mainly in preoptic area of hypothalamus (critical for nurturing behaviour)
• fosB-deficient mice: normal motor behaviour, normal levels of reproductive hormones and intact glands—not a pleiotropic effect

Question 27

where does gene expression act?

Answer 27

at 3 diff phenotypic levels

Question 28

what can expression of a gene influence?

Answer 28

expression of other genes

activity of the cell, other tissues and organs

developmental processes

activity of brain, muscles, messenger systems→ expression of behaviour

Question 29

what do env influences act on?

Answer 29

gene expression and/ on phenotype

Question 30

what are traits determined by?

Answer 30

genes and env in conjunction - continuous variation

Question 31

what can quan traits be?

Answer 31

morphological

physiological

behavioural

Question 32

norm of reaction

Answer 32

Pattern of phenotypic expression of a single genotype across a range of environments

Question 33

what is total phenotypic variance (VT) in a trait based on?

Answer 33

additive effects of genetic variance (VG)

environmental variance (VE)

VT = VG + VE

Question 34

trait heritability

Answer 34

h2 = VG / VT

proportion of phenotypic

variance associated with genetic variance

N.B. heritable ≠ ‘genetically determined’

Question 35

artificial selection of heritable traits

Answer 35

h2 = R/S

h2 = 0 (no resemblance)

h2 = 1 (full resemblance)

Question 36

artificial selection: rats selected for maze-running ability

Answer 36

Effects of genotype can be masked by environmental effects

enriched environment improved performance of maze-dull rats

restricted environments prevented expression of inherited ability

Question 37

genetic mutation

Answer 37

Most mutations are harmful or neutral in their effects; only rarely are mutations beneficial

Alleles at >1% frequency termed wild-type

Alleles at <1% frequency
termed mutant

Gene with one wild-type allele is monomorphic

Gene with >1 wild-type allele is polymorphic

germ-line = whole body - gametes carry mutation

somatic = certain area - gametes don’t carry mutation

Question 38

what increases mutation rate above spontaneous level?

Answer 38

mutagens and radiation

Question 39

examples of mutagens and radiation

Answer 39

Oxidative radicals

Intercalating agents cause single-nucleotide insertions/deletions

shorter wavelength (high-energy) radiation capable of inducing mutations in DNA

Question 40

example of genetic mutation

Answer 40

social amnesia is related to mutation in single gene

Oxt−/− males cannot produce oxytocin
- continue acting same way towards female even when already met her

Question 41

identical twins

Answer 41

monozygotic

Genetically identical

Shared same early (pre-natal) rearing environment

Shared same late (post-natal) rearing environment

Question 42

non-identical twins

Answer 42

dizygotic

Genetically different

Shared same early (pre-natal) rearing environment

Shared same late (post-natal) rearing environment

Question 43

adopted children

Answer 43

Genetically different

Different early (pre-natal) rearing environment

Shared same late (post-natal) rearing environment

Question 44

nature v nurture

Answer 44

Genetic factors contribute to individual differences in general cognitive abilities

A = additive genetic variance, heritability (i.e. effect if you substitute one allele for another) - plays biggest role