PSY 213 Lecture Notes - Lecture 3: Quantitative Trait Locus, Mendelian Inheritance, Y Chromosome
Chapter 3 – Biology and B’ PSY 213
JAN 15/18
Themes
Nature + nurture
Brain devel’
The body: Physical growth + devel’
- Nature and nurture
- The active child
- Continuity/discontinuity
- Mechanisms of change
- Individual differences
- Research and children's welfare
Nature + Nurture
- Genetic + Environmental Influences
- The interplay be/n genes + experience v. complex
- Genotype: genetic material an individual inherits
- Phenotype: observable expression of the genotype, including body characteristics
+ b’
- Environment: every aspect of the individual, + his/her surroundings other than
genes
Relation 1: Parents’ + Child’s Genotypes
- Genetic material is passed on as chromo (long, threadlike molecules made up of DNA)
from parent to offspring
- Genes (sections of chromo) are the basic units of heredity for all living things; 2% of
human genome
- Sex chromo determine an individual’s sex
- Females have two X chromo in the 23rd pair, males have an X + Y chromo
- A gene on the Y chromo encodes the protein that triggers the formation of the
testes which subsequently produces testosterone + then take over the moulding of
maleness
Human Heredity
- Color-enhanced micrograph (karyotype), shows the 23 pairs of chromosomes.
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Chapter 3 – Biology and B’ PSY 213
JAN 15/18
- In nearly all cases, the chromosomes of each pair are roughly the same size except the
sex chromosomes (middle of bottom row)
- The Y chromosome that determines maleness is much smaller than the X
chromosome.
- Obtain genetic diversity through mutations, random assortment, & crossing over.
- Regulator genes largely control the
continuous switching on and off of genes
that underlie development across the life
span.
- A gene influences development and behaviour only when it is turned on & external
factors can affect the switching on & off of genes.
Relation 2: Child’s Genotype + Phenotype
About 1/3rd of human genes have 2 or more different forms, known as alleles.
Mendelian inheritance patterns
- for the offspring of two brown-haired parents who are both heterozygous for hair color.
- The allele for brown hair (B) is dominant, and that for blond hair (b) is recessive.
- These parents have 3 chances out of 4 of producing children with brown hair & two
chances in four of producing brown-haired children who carry the gene for blond hair.
Polygenic inheritance – most traits & behaviours
- Occurs when traits are governed by more than one gene
- Involves several different genes that contribute to any given phenotypic outcome
- Examples: shyness, aggression, thrill-seeking, and language learning
Relation 3: Child’s Enviro + Phenotype
Norm of reaction
- All phenotypes that could theoretically result from a given genotype, in relation to all the
environments in which it could survive and develop
- Over 5,000 human diseases and disorders are presently known to have genetic origins but
environment remains a factor in how they develop
Relation 4: Child’s Phenotype + Enviro
Children are active creators of the environment which they live
- By virtue of their nature + b’, they evoke responses from others
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Chapter 3 – Biology and B’ PSY 213
JAN 15/18
- They also actively select surroundings + experiences that support their interests, talents, +
characteristics
- When young, parents shape enviro for children
- As we age we get to shape our own enviro more + more
I.e. child may bring a parent a book indicating they want to read be/c they like it
- Friends can influence enviro
Relation 5: Child’s Enviro-Child’s Genotype
Epigenetics
- Although structure of DNA remains fixed, certain epigenetic mechanisms (eg.
Methylation), mediated by environment, can alter gene function + create stable changes
in their expression
- Differences in identical twins
- 3yr olds: virtually no diff in methylation
- 50yr olds: remarkable differences
- Poor maternal care + stress coping
B’ Genetics: Research Designs
Concerned w/how variation in b’ + devel’ results from the combination of genetic +
environmental factors
Family study
- Measure trait of interest among people who vary in genetic relatedness
Correlations be/n the measure of the trait in individuals w/different rel’ships
- Examined to see if they are higher for individuals who are genetically more similar +
who share the same enviro
Brain Devel’
- Structures of the brain
- Developmental processes
- The important of experience
- Brain damage + recovery
Structure of the Brain
Neurons are specialized cells that are the basic units of the brains info system
- Cell body: contains the basic biological material that keeps the neuron functioning
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Document Summary
The interplay be/n genes + experience v. complex. Phenotype: observable expression of the genotype, including body characteristics. Environment: every aspect of the individual, + his/her surroundings other than genes. Genetic material is passed on as chromo (long, threadlike molecules made up of dna) from parent to offspring. Genes (sections of chromo) are the basic units of heredity for all living things; 2% of human genome. Females have two x chromo in the 23rd pair, males have an x + y chromo. A gene on the y chromo encodes the protein that triggers the formation of the testes which subsequently produces testosterone + then take over the moulding of maleness. Color-enhanced micrograph (karyotype), shows the 23 pairs of chromosomes. In nearly all cases, the chromosomes of each pair are roughly the same size except the sex chromosomes (middle of bottom row) The y chromosome that determines maleness is much smaller than the x chromosome.
