L2 slides - Genetics, Learning, and Development

Phenotype and Genotype

• Phenotype: manifestation of traits in an individual, encompassing morphology, physiology, and behavior.

• Genotype: genetic makeup of an individual, represented by allelic combinations including SNPs, genome duplications, inversions, etc.

• Environment: non-genetic factors influencing an individual, which can be ecological (e.g., temperature, nutrients) or social (e.g., experiences, group size).

• In psychology, behavior is represented as:

  • Behavior = Nature + Nurture

  • Phenotype = Genotype + Environment

Gene Expression and Behavior

• DNA in somatic cells is mostly unchanging.

• Gene expression (transcription and translation) is influenced by both internal factors (e.g., age, cell differentiation) and external cues (e.g., social and ecological environments).

• The production of peptides or proteins from activated genes can lead to behavioral changes, mediated by substances like hormones and neuropeptides.

Epigenetics and Gene Regulation

• Epigenetics: refers to chemical modifications on DNA or histones that can affect transcription levels without altering the DNA sequence.

• miRNA: a small, non-coding RNA molecule that plays a role in regulating gene expression by repressing translation or facilitating mRNA degradation, functioning beyond DNA sequences.

Genetic Approaches

• Forward Genetics (Observational): Identifies genes associated with a specific phenotype (e.g., Whitfield et al. 2003).

• Reverse Genetics (Experimental): Investigates phenotypes resulting from specific alleles or combinations (e.g., gene knockout, CRISPR).

• Follow-up studies have clarified causal relationships between certain genes and behavioral shifts (e.g., honeybee behavior from nursing to foraging).

• Reminder: correlation does not imply causation (e.g., "Eating ice cream causes sunburn!").

Key Takeaways of PART 1

• Behavioral development is driven by changes in gene expression.

• Worker Bee Behavior Development: affected by both internal (age) and external (social environment) factors leading to differences in gene expression and, thus, behavior.

• Queen vs. Worker Bee Differentiation: differentiation arises from dietary influence where the same genotype can yield either phenotype (a queen or worker) based on nutrition.

• Epigenetics: diet contains miRNA that regulates post-transcription gene expression.

Trait Variation

• Genetic Variation (G): determined by heritable genes (e.g., base skin color from parents).

• Environmental Variation (E): not heritable changes based on environmental influences (e.g., skin tanning due to sun exposure).

• Genotype by Environment (G x E) Interaction: example where light-skinned individuals tend to burn more easily, while dark-skinned individuals can tan more efficiently.

Alternative Behavioral Phenotypes

• Existence of multiple behavioral phenotypes within the same species (e.g., worker and queen bees).

• Often utilized to study proximate mechanisms behind behavioral variations due to their discrete nature.

• Can arise from environmental influences (behavioral polyphenism) or genetic differences (behavioral polymorphism).

Behavioral Polyphenism

• Examples include:

  • Worker vs. Queen

  • Territorial vs. Non-Territorial

  • Anti-predator defense vs. No defense

• Phenotypic Plasticity: ability for the same genotype to exhibit different phenotypes based on varying environments, which can be categorized as high, low, or multimodal.

• Polyphenism: a specific type of phenotypic plasticity leading to discrete phenotypes arising from a single genotype.

Key Takeaways of PART 2

• Behavioral differences across individuals, populations, or species result from genetic differences (G), environmental variations (E), or their interactions (G x E).

• Experimental designs such as common garden, reciprocal transplant, and cross-fostering aid in disentangling these influences.

• Within a species, behavioral variations can stem from either genetic (behavioral polymorphism) or environmental factors (behavioral polyphenism).