Behavioural Genetics

Question 1

Behaviour

Answer 1

Behaviour is a complex topic of study in humans. Individuals vary in the phenotype of mental
disorders. Some human behaviours have been shown to have a clear genetic component.

Question 2

Fragile X

Answer 2

triplet repeat CGG and is more frequently observed in males

Question 3

Huntington’s and genetics

Answer 3

Huntington’s disease is associated with
the number of CAG repeats.

Question 4

Alzheimer’s and genetics

Answer 4

Alzheimer’s associated with a build of plaques, early and late onset.

Associated with locus on chromosome 21.

Apolipoprotein; three E alleles. ApoE4 homozygotes have earlier age of incidence of Alzheimer’s.

Question 5

Genetics of human behaviour and twins

Answer 5

The genetic correlation of monozygotic (MZ) twins is 1.0 verses 0.5 for dizygotic (DZ) twins. Can ask
how similar a behavioural trait is in MZ or DZ twins. The argument is that DZ and MZ twins have the same environment and therefore only differ in their genetic makeup.

Twin studies have been used in the study of human behaviour such as schizophrenia. The relative risk of having schizophrenia if a relative also has it increases with relatedness. GWAS studies have revealed loci associated with the disease.

Question 6

Autism and genetics

Answer 6

Autism associated with many traits including poor social behaviour, language skills repetitive
behaviour. Many loci are involved often associated with deletions.

Question 7

Genetics of animal behaviour

Answer 7

Many behavioural (and morphological) traits can be selected for by breeding the extremes of a
character over several generations. A classic example of artificial selection can be seen with the diversity of dog pedigrees. Pit-balls bred to bite and hold; Pyrenean Mountain dog to be large and frighten off wolves.

Question 8

Genetics and silver foxes

Answer 8

Silver foxes are an interesting example to selection on extreme behaviour. If you have wild
population of silver foxes, artificially selecting for the friendliest foxes can produced domesticated
foxes after only 15 generations. As foxes became tamer, coincided with changes in the coat colour of the foxes.

Question 9

The genetics of IQ

Answer 9

There are many different tests for IQ and the attribution of IQ scores to genetics is of interest to scientists, journalists and public alike. There is certainly heritability in IQ as shown in twin studies.

However, dissociating the effects of the environment is very difficult, as shown in adoption studies.

Mean IQ in Britain has been increasing since the development of the measure. Income has a strong effect on IQ in the USA. Heritability in IQ increases with age.

Recent GWAS studies have found no association between IQ and SNP variation.

Studies looking at differences in IQ between different races often fail to take into account the
interaction between genes and environment