- Physical development, nervous system -> genetic blueprint from our
- Biological characteristics and environmental forces determine our
Chromosomes and genes
- How genetic transmission passed down? Semi-correct answer
provided from Hippocrates.
- Gregor Mendel, a monk, marked the beginning of modern genetic
- Produce visible characteristics of possible transmission to another
- Genotype: specific genetic makeup of an individual. Sometimes used,
not used, varied.
- Phenotype: observable characteristics. Can be affected by other
genes & environment.
- 2 cells (eggs & sperm) carry the material of heredity –
chromosomes, is the beginning of a new individual: zygote.
- Chromosomes: tightly coiled molecule of DNA partly covered by
- DNA: (deoxyribonucleic acid) carried the heredity blueprint in unit
- Genes: carries info about your characteristics, potentials and
- Every cell has 46 chromosomes – except the sex cell (has 23)
because egg & sperm = 46.
- Each cell in your body contains the genetic code for your entire body.
- Alleles: alternative form of a gene that produces different
- Genes affect our body’s development & functioning through one
general mechanism: genes code for the production of proteins (est. 70
000 different types)
- Proteins: control the structure of individual cells and all the chemical
reactors necessary to sustain the cell.
- ~1/2 genes target brain structure & function.
- Each gene carries the code for a specific protein.
- A gene can, at different metabolic and environmental factors,
activate and deactivate levels of specific protein.
- As the protein levels change, there is a corresponding change in
function of that neuron & neural circuits.
Dominant, recessive & polygenic effects p.111 - Some genes are dominant and some are recessive.
- Dominant: particular characteristic will be displayed.
- Recessive: characteristic will not show up (unless both genes are
- Both D&R can be passed on but R usually remains hidden.
- Polygenic transmission: picture that would occur if all characteristics
were determined by one pair of genes. Also magnifies the number of
possible variations in a trait that can occur.
- Human genes are 99.9% identical: union of sperm & egg can result
in about to trillion potential genotypes.
Mapping the genetic code
- Genetic structure has been mapped by using methods to disassemble
the genes on each chromosome & study the specific sequence of
substance that occur in each gene: A, T, C & G (Adenine, Thymine,
Cytosine & Guanine) = 3.1 billion.
- Humans have fewer genes than expected: 25 000 not 100 000.
- Apx. 200 human genes may have arisen from genes that bacteria
inserted into our early ancestors.
Genetic Engineering: The Edge of creation p.112
- Recombinant DNA procedures: use certain enzymes to cut the long
thread like molecules of genetic DNA into pieces, combine them with
another organism and insert them into a host organism.
- Recent gene-modification research by psychologist has focused on
processes such as learning, memory, emotion & motivation.
- Gene knockout: particular function of a gene is eliminated. Help
determine the importance of particular transmitter substance in
relation to the behaviours of interest – doesn’t mean a singular gene is
- Very little behaviour is controlled by a singular gene.
IN REVIEW p.112
- DNA carries 23 pairs of chromosomes in genes.
- Some genes are dominant/some are recessive.
- Genes influence development, structure & function.
- Genetic engineering allows scientists to duplicate (alter) genetic
material or to repair dysfunctional genes.
Behaviour genetics techniques p.113
- Probability of sharing any particular gene with one of your parent is
50%, grandparents 25%.
- Heritability coefficient: Extent to which variation in a particular
characteristic within a group can be attributed to genetic factors. - Heredity: passage of characteristics from parents to offspring by way
- Heritability: how much of the variation in a characteristic within a
population can be attributed to genetic differences.
Differences/variance in trait across individuals.
- Concordance/co-occurrence: possible genetic contribution.
- Adoption study: Adapted earlier & compared on some characteristic
both with the biological parents & with adoptive parents.
- Twin studies: More powerful techniques used in behavioural genetics.
- Monozygotic: Identical twins develop from the some fertilized egg,
genetically identical. 1/250 births.
- Dizygotic: fraternal twins develop from two fertilized eggs, share
50% of genetic endowment like other siblings. 1/125 births.
- Many psychological characteristics, including IQ, personality, psyc.
Disorders have a notable genetic contribution.
- Genetic & environmental factors almost always interact with each
other to influence behaviour.
IN REVIEW p.116
- Genetic & environmental factors in psychological traits & behaviours.
- Major studies are adoption & twin studies.
- Most useful research is the study of identical & fraternal twins from
two different environments.
- Behaviour genetics techniques allow a heritability coefficient to be
determined for different characteristics.
- Heritability coefficient indicated the extent to which variation in a
particular characteristic can be attributed to genetic factors.
Genetic influence on behaviour p.117
- Individual characteristics as individuals = experience & environment
= acting on our genetic makeup.
- All behaviour = reflect genes & environment.
- Study of genes – environment interaction from studies of intelligence
Heredity, environment & intelligence
- The more genes people have in common the more similar they are in
Biological reaction range, the environment, personality &
- Reaction range: range of possibilities that the genetic code allows.
- 2 factors influence our potential our genetic inherence & the
opportunities our environment provides for acquiring intellectual skills. This also depends on our own interest; motivation & personal
characteristics --> affect how much we apply.
Behaviour genetics & personality
- Personality could be traced. Difference in brain development or
- Personality trait theory: Five Factor Model believe that individual
differences in personality can be accounted for by variation along 5
1. Extraversion – Introversion (sociable, outgoing, adventuresome)
2. Agreeableness (cooperative, helpful, good-natured)
3. Conscientiousness (responsible, goal-directed, dependable)
4. Neuroticism (worrying, anxious, emotionally unstable)
5. Openness to experience (imaginative, artistically sensitive)
- Generic factors account for a significant amount of personality
1. Variation attributable to genetic factors.
2. Variation due to a shared family environment among those reared
3. Variation attributable to other factors (ex: individual experiences)
- Minnesota Twin Study – 400 pairs of twins: environment accounted
for little to no variation.
- Genes control development & function of physical characteristics all
IN REVIEW p.123
- (+) correlation between similarity genetics & IQ. (&important
- Genes give us a reaction rage yet our IQ depends on environment
- Identical twins > fraternal twins.
- Genetic fact