Chapter 3 - Biology and Behaviour

genome

* the complete set of DNA of any organism, including all of its genes

comparisons of genomes of various species have revealed that

1. humans have roughtly 20-21k protein-coding genes
2. genes are possessed by all living things
3. genes make up only about 1% of the human genome

genotype

genetic material an invididual inherits.

phenotype

the observable expression of the genotype, including both body characteristics and behaviour.

environment

every aspect of individuals and their surroundings other than genes.

5 relations are fundamental in the development of every child

1. parents genotype-child’s genotype
2. child’s genotype-child’s phenotype
3. child’s environment-child’s phenotype
4. child’s phenotype-child’s environment
5. child’s environment-child’s genotype

genes

* the basic unit of heredity in all living things.

what do genes guarantee?

* humans will be similar to each other at the species level and at the individual level.
* differences that contriubte to genetic diversity

random assortment in chromosomes

* 23 chromosomes are shuffled randomly, with only chance deciding which pair goes into each new egg or sperm

crossing over

* DNA switches from one chromosome to the other, resulting in some of the chromosomes of the parents different than their own

mutations

* changes in a section of DNA
* These mutations are either random errors caused by environmental factors or from inherited disorders.
* Most are harmful, but some increase disease resistance and allow individuals to adapt to crucial aspects of the environment.

sex chromosomes

* the chromosomes (X and Y) are chromosomes that determine an individual’s designated sex at birth.

endophenotypes

Genes that influence unobservable, intermediate aspects of the phenotype that impact behaviour, our brain and nervous systems

regulator genes

genes that control what genes turn on and off in patterns

this results in large diversity in genetic expression

alleles

2 or more different forms of a trait

homozygous

2 dominant or 2 recessive alleles inherited

heterozygous

1 dominant and 1 recessive inherited allele

* the dominant allele will be expressed

phenylketonuria (PKU)

* a disorder related to a defective recessive gene on chromosomes that prevents metabolism of the amino acid phenylalanine.

Parent’s contributions to the child’s environment

* Parent’s behaviour towards children is genetically influenced along with the preferences, activities, and resources to which they expose their children.

Child’s Phenotype - Child’s Environment

* Children create their own environments by actively selecting surroundings and experiences that match their interests and personalities.
* Children’s ability to shape their own environments has profound effects on intellectual development.

Child’s Environemnt - Child’s Genotype

* Epigenetic mechanisms are mediated by the environment, and can alter the functioning of genes and create stable changes in their expression. These changes can be passed onto children.

methylation

works like a dimmer switch with methyl molecules blocking transcription in the promotor region of the gene in order to turn off gene activity

behaviour genetics

* the science concerned wtih how variation in behaviour and development results from the combination of genetic and environmental factors.

heritable

genetically transmitted

2 premises used to differentiate genetic and environmental contributions

* (1) If genetic factors are important for a given trait/behaviour, people who are genotypically similar should be phenotypically similar.
* (2) If shared environemntal factors are important, people who were raised together should be more similar than people who were raised apart.

Quantitative behaviour geneticists use…

* stats to study *naturally occcuring genetic and environmental variation* in a population by studying the phenotypes of people who differ in the amount of genomic DNA they share.

Family study design

* Quantitative behaviour genetics research is used to determine whether phenotypic traits are correlated with the degree to which people are genetically related.

Twin-study design

* This design is used to compare correlations for identical twins with those for same-sex fraternal twins.

Equal environments assumption

* Both types of twins shared the same prenatal and postnatal environment (in the terms of family and community), so if the correlation between identical twins on a given trait/behaviour is significantly higher than the correlation between fraternal twins, genetic factors are mainly responsible.

Adoption study design

* Researchers examine whether adopted children’s scores are correlated more highly with those of their biological relatives or with those of their adoptive relatives.

Heritability

* a statistical estimate of how much of the measured variance on a phenotypic trait among individuals in a given population is attributable to genetic diferences among those individuals.
* Some heritable traits are temperament, aspects of personality, cognition, and psychopathology.

Molecular behaviour geneticists examine…

* specific DNA sequences to identify mechanisms that link genes and behaviour.

Genome-wide association studies (GWAS)

* are used to link multiple DNA segments with particular traits.

Genome-wide complex trait analysis (GCTA)

* uses genetic resemblance across large groups of individuals to make it possible to differentiate aspects of genes and environment that are confounded within families.

cell body

* contains basic biological material that keeps the neuron functioning

dendrites

* neural fibers that recieve input from other cells and conduct it toward the cell body in the form of electrical impulses

axon

* neural fibers that conduct electrical signals away from the cell body to connections with other neurons

synapses

* junctions between the axon terminal of 1 neuron and the cell body of another neuron.

glial cells

cells that form a myelin sheath

* function as a neutral stem and progenitor cells, protecting the brain and potentially aiding in regeneration when injured

myelin sheat

* a fatty sheath that increases the speed and efficiency of information transmission

cerebral cortex

* 80% of the brain and consists of 4 lobes - the frontal lobe, the parietal lob, the temporal lobe, and the occipital lobe.

occipital lobe

* primarily involved in processing visual information.

temporal lobe

* associated with speech, language, music, and emotional information.

parietal lobe

* associated with spatial processing and sensory info integration.

frontal lobe

* associated with working memory and cognitive control.

association areas

lie between the major sensory and motor areas

cerebral hemispheres

* Sensory input from one side of the body goes to the opposite side of the brain.

corpus callosum

* dense tract of nerve fibers.

\

cerebral lateralization

* the specialization of the hemispheres of the brain for different modes of processing (ex. right hemispheres for faces, left hemispheres for speech).

Neurogenesis

* the proliferation of neurons through cell division

Myelination

* the formation of myelin around the axons of neurons that speeds and increases information-processing abilities (white matter)

synaptogenesis

* the process by which neurons form synapses with other neurons, resulting in trillions of connections.

synpatic pruning

* the normal developmental process through which synpases that are rarely activated are eliminated.

plasticity

* the capacity of the brain to be affected by experience.

during specific periods…

* the human brain in especially sensitive to specific external stimuli, and the neural organization that occurs (or does not occur) during these periods is typically irreversible.

experience-expectant processes

* The process where normal wiring happens just because of the individual being a member of the species.

exprience-dependent processes

* The process through which neural connections are created and reorganized throughout life as a function of an individual’s experiences.

infant feeding

* Breast milk is naturally free of bacteria, strengthens the infant’s immune system, and contains important antibodies.
* It also has a positive effect on cognitive development, which leads to higher IQ scores.
* For those in countries with unsafe drinking water and fewer public health resources, breast-feeding is essential in promoting positive health outcomes.

Food preferences

* Some food preferences are innate.
* Infants develop a preference for some tastes after 4 months of age
* they are influenced by prenatal environment and flavour of breast milk

neophobia

* an unwillingness to eat unfamiliar foods.

Why ar some overweight but not others?

* Genetic and environmental factors play roles in this.
* Genetic factors are proven in the findings that (1) adopted children’s weight is more correlated with biological parents than adoptive parents (2) and identical twins raised apart have more similar weight than fraternal twins.
* POMC - a genetic deletion - can lead to human obesity.
* Childhood impulsivity also leads to obesity.

Environmental factors that contribute to obesity

* A lack of physical education programs, recess activities, healthy cafeteria lunches.
* Children spend less time outside and more with screens.
* Less sleep because children spend more time on screens.
* Unhealthy food is cheaper and more readily available than healthy food.

Social treatment of obese children

* Obese children are more likely to struggle with friendships and are generally poorly treated by peers.

\

Undernutrition

* associated with poverty, limited access to healthcare, warfare, famine, natural disasters.

Vaccines

* deliver a weak version of the disease to the to promp the body to produce anitbodies to attack it.
* Antibodies provide protection against subsequent encounters with disease.
* Some parents believe vaccines are harmful and refuse to take them or to let their children take them.
* This creates a risk for children and others in the community.
* Some vaccines operate on *herd immunity*, meaning a certain population needs to be vaccinated for it to work, so this behaviour can lead to several deaths.