Behavioural Genetics: Are Genes Involved?

Importance of selection and inbreeding studies in elucidating genetic influences on behavior.
Specific studies conducted on mice to assess behavioral genetics.

Definition: Domestication syndrome refers to physical and behavioral changes in species during domestication.
- Comparison of single nucleotide polymorphisms (SNPs) in free-breeding vs pure-bred dogs.
- Found enrichment in genes associated with the sonic-hedgehog (SHH) pathway, which is crucial for adhesion and migration of neural crest cells.
- States that not all dogs are selected, leading to significant genetic differences.

The SHH pathway is instrumental in various developmental processes, particularly in neural crest cell development.
Historical Context:
- Controls processes related to cell adhesion and migration in development.

The presence of aberrant activation (mutations) in the SHH pathway can lead to various cancers, such as:
- Medulloblastoma
- Rhabdomyosarcoma
- Basal cell carcinoma
- Glioblastoma
- Cancers of the lung, colon, stomach, pancreas, ovary, and breast.
Developmental problems tied to SHH mutations include:
- Nonsyndromic holoprosencephaly
- Coloboma
- Microphthalmia
Mutations can also lead to major disruptions, reaffirming the importance of studying naturally occurring variations in the context of liability thresholds.

Knowledge in developmental biology and cell biology is essential to understanding behavioral genetics, particularly concerning the SHH pathway.
Variations in SNPs may change binding affinities in crucial proteins, impacting behavior.

Utilization of ‘open field’ tests to measure activity levels in mice as an indicator of fearfulness.
- Lower activity in the open field box correlates with higher fear levels.
Interpretation of activity levels informs our understanding of genetic variability among different mouse strains.

High Control vs Low Multigenetic Traits:
- Traits were found to be genetically inherited, demonstrated by consistent selection results across generations.
- The differences between low and high activity mice increased with each generation, indicating a multi-genic trait.
Discussed genetic models:
- **Single Gene Influence:
- 1 gene leads to 2 alleles and 3 genotypes, resulting in 3 phenotypes.
- 2 genes lead to 2 alleles and 9 genotypes, resulting in 5 phenotypes.
- 3 genes lead to 2 alleles, 27 genotypes, resulting in 7 phenotypes.**
The greater the number of genes involved, the more uneven the distribution of phenotypic traits, creating a normal distribution curve.
- Multiple genes can show additive effects, leading to a plateau in the distribution graph, making extreme traits more evident.

Questions arise regarding why complex disorders like schizophrenia are considered qualitative when influenced by many genes.
- Liability Threshold Model:
- Symptoms are diagnosed following a specific severity level achieved, implicating additive gene influences.

Overview of inbred strains of mice as a method of studying genetic inheritance:
- Examples include strains such as BALB/c, DBA/2, C3H/2, and C57BL/6, all genetically identical through brother-sister matings.
Evidence indicates that genetic differences directly influence behavior in a controlled environment
Inquiry posed regarding the significance of the F1 generation in genetic studies:
- It represents the first filial generation of offspring in breeding experiments.

Understand and describe the sonic hedgehog pathway and its implications.
Comprehend how selection and inbreeding studies reveal genetic and environmental influences on behavior.
Be capable of interpreting results from F1 and B1 progeny in genetically controlled environments.

The intersection of genetics and behavior is complex, encompassing genetic, biological, and environmental factors that shape the development and characteristics of behaviors in animals and humans alike.