U03 - Genetics & Evolutionary Foundations of Behavior Flashcards
Genome
The entire sequence of our DNA
- complete set of genetic material; the “blueprint” for making & maintaining an organism
DNA
molecule that carries genetic information, organized and packaged within chromosomes
- DNA is composed of hundreds of thousands of genes
Chromosomes
we carry 2 copies of the genome, which means that in most human body cells we have two pairs of 23 chromosomes, 46 total
- molecule that carries genetic information, organized and packaged within chromosomes
- rod-shaped structures that reside in a cell’s nucleus
- A chromosome is composed of complex double strands of deoxyribonucleic acid (DNA)
Gene vs alleles
gene:
- segment of DNA that codes for a particular protein
Humans have 2 versions (alleles) of each gene, 1 from each parent
- A variant form of a gene; humans have two alleles per gene, one inherited from each parent.
dominant vs recessive allele
Alleles influence a phenotype by having a strong (dominant) or weak (recessive) influence.
genotype vs phenotype
genotype
- the genetic makeup of an organism composed of the organism’s compete set of genes
phenotype
- observable characteristics of an individual, produced by interaction of genotype and environment
homozygous vs heterozygous
homozygous: NN or nn, two dominant alleles, dominant shows, or two recessive alleles, recessive shows
heterozygous: one dominant and one recessive allele, dominant trait shows
how genes affect behavior
- Genes do not directly code for a behavior or trait
- Genes code for proteins, which contribute to physical structures & functions of the body, including the brain
- Multiple genes are involved in giving rise to complex mental states, behaviors, & traits
Candidate gene study
- compare individuals with the candidate gene with individuals without on a given trait or disorder
- candidate gene study: a gene that is believed to be related to a particular trait, such as a disease or a physical attribute
limitations:
- Typically correlational in nature, Other factors, like other genes, cannot be ruled out
- Underestimate biological complexity of multifaceted traits & behaviors
gene knockout vs gene knockdown
knockout:
- remove or deactivate gene
knockdown
- make gene less active
- study: mice who don’t miss mom after knockdown of the gene u-opioid
genome-wide association studies
- Instead of looking at single gene (or small set of genes), scan entire genome & look for associations with particular phenotype
- limitations:
- false positives
- biological relevance often not clear
- still correlational
diathesis-stress vs differential susceptibility model
diathesis-stress:
- some individuals have a predisposition (diathesis) that makes them more vulnerable to negative environmental influences (e.g., stress)
- The diathesis-stress model states that people with a strong genetic predisposition for a given health condition will be more sensitive to having that condition triggered by a stressful environment.
differential susceptibility:
- some individuals are more sensitive to both negative and positive environmental influence
- The differential sensitivities hypothesis suggests that some people have a genetic predisposition to be more strongly affected by their environment (both stressful and supportive conditions).
gene expression
- Environmental factors affect which genes are turned “on” and “off
- what influences it:
- social environments
epigenetic change
- type of change to structure of DNA that affects gene expression without altering the underlying DNA sequence
- study: rat moms
study: rate moms, epigenetic change
Michael Meany and colleagues studied the effects of different parenting styles in rats. They found that pups of high licking and grooming (high LG) moms are less reactive to stress, both behaviorally and physiologically, due to increased receptors in the hippocampus, which helps regulate stress. Pups born to low LG moms but raised by high LG moms develop similar low stress reactivity and even become high LG moms themselves, showing that this behavior can be passed on across generations without genetic influence.
- The point of Michael Meany’s study is to show how epigenetic changes can occur due to early-life experiences, like parenting. The differences in stress reactivity in rats are not caused by genes but by changes in how genes are expressed based on the mother’s behavior. High licking and grooming (high LG) causes changes in the brain that reduce stress, and these changes can be passed across generations, not through DNA but through behavior and environment. This demonstrates how epigenetics (environmental influences on gene expression) plays a key role in development.
