3. Behaviour Genetics Flashcards
Why is there considerable variation in behaviour amongst individuals within a species?
- Genetic differences
- Environmental experiences
What is heritability an indication of?
How much a character or trait in an individual is likely to be passed on to its offspring
To what extent is behaviour heritable?
The majority of behavioural traits are only 10-28% (0.10-0.28) heritable
- Meaning, most of the determinants of a behaviour are environmental, or due to some aspect of an animal’s experiences
- In contrast to growth or fertility traits which can be 0.40 heritable
What is behaviour genetics? What do behaviour geneticists study?
- Field of study that examines the role of genetics in animal behaviour
- Behaviour genetics is highly interdisciplinary, involving contributions from biology, genetics, ethology, psychology, and statistics
- Behaviour geneticists study the inheritance of behavioural traits, often using twin studies, breeding, transgenesis, or gene knockout techniques
Why is behaviour heritability so low?
Genes affect traits, but this does not mean that a single gene controls it, as most behaviour traits are affected by many genes (polygenic)
- While most behaviour is not monogenic, a single gene can have a crucial role for the normal appearance of a behaviour pattern
Genes associated with particular behaviour traits can be inherited (very frequently) together with some other trait such as…
An anatomical feature
- eg. the gene affecting the behaviour trait and that affecting the anatomical trait are ‘linked’
- may be close together on the same chromosome so they are unlikely to be separated by crossover during meiosis
What are 3 examples of single gene influences on behaviour?
*this is rare for a single gene to influence behaviour
1. Agouti gene and aggression in mice
2. Struggling when being restrained
- more pronounced in Basenjis
3. Tendency to bark (inherited via 2 genes)
- Basenjis have very high bark threshold
How can behaviour genes be localized?
- First, we localize the position on the chromosome related to the phenotypic expression of the behaviour
- Behaviour may be inherited in close correlation with some other trait for which the gene location is known (linkage) - Can use quantitative trait loci (QTL) analysis or genome-wide association studies (GWAS)
- The genome of animals are mapped with respect to the occurrence of specific DNA markers, which vary between individuals in specific chromosomal locations
- The correlation btw a particular behaviour trait and the occurrence of different markers can be assessed; implies the gene that affects the trait is located close to that marker
What is the role of evolution in terms of behaviour?
The mechanisms that control behaviour have evolved by natural selection just like any other characteristic of living organisms
Natural selection acts on animals so as to…
Natural selection acts on animals so as to increase the proportion of some genes in the population at the expense of others
Inclusive fitness
Refers to gene frequency in terms of the effects of that gene on individuals (usually related)
- This is in contrast to individual fitness, which refers to the number of offspring of that individual which themselves survive to breed
- In inclusive fitness, some genes affect the survival of relatives
Artificial selection
In contrast to natural selection, artificial selection is when we select for characters or traits we find desirable, so as to increase the gene frequency of those traits in a given population (eg. in a herd)
- eg. increasing growth rate in cattle or pigs, or selecting for increased milk production in dairy cows (remember, growth traits are very heritable)
- In comparison, what happens when we artificially select for behavioural traits, which are less heritable
What did Paul Siegel do?
- Behaviour genetic analyses in chickens and quail
- High mating freq line and low mating freq line over generations; successfully got a divergence and created 2 different lines of roosters
- Low line had really high heritability. Why? Although hard to cheat high performing, but any one thing doesn’t go right and you get low (not very reliable)
What is meant by “behaviour as a secondary trait”?
Sometimes, in the process of artificially selecting for one trait (eg. increased growth rate), a second trait is inadvertently selected for as well (eg. aggression)
