Developmental - Lecture 7 - Biological psychology (week 7) Flashcards
- Explain basic genetic mechanisms
Within each cell is a nucleus (except red blood cells).
Each nucleus contains 46 chromosomes, arranged in 23 pairs.
Each chromosome is made up of long chains of DNA –molecules (DNA=deoxyribonucleic acid).
Genes are small sections of DNA, consisting of chemical bases arranged in triplets.
Genes instruct the cell to manufacture proteins.
Proteins build new body cells and regulate cell function, thus underlying human growth and development.
Genes are known, collectively, as the genome:
Genome = the full set of genes present within a cell to make a new human being.
Humans have ~25,000 genes located on 46 chromosomes (i.e. in each cell!).
Large proportions of the human genome are 99.9 % identical for any two persons!
Also: some human and nonhuman genomes are largely identical: e.g., chimps and humans = 98-99%.
- Describe genetic contributions to sex and individual differences
Starts with reproductive cells, called gametes (male gamete = sperm; female gamete = ovum/egg)
The gametes only contain 23 chromosomes each (not 46 as in other cell types).
During fertilisation, sperm and ovum unite to form a zygote with 46 chromosomes.
CONTRIBUTIONS: The 23rd pair of chromosomes is the sex chromosome (XX = female, XY = male).
Genotype = the genetic material an individual inherits.
Phenotype = observable characteristics of a person, including appearance, personality, intelligence, and other traits inherited through the genotype.
What accounts for individual differences in gene expression (i.e. in phenotype)?
Alleles - Variations in the chemical arrangement of some genes. These variations can cause differences in a person’s phenotype.
Dominant – Recessive Genes (or Alleles) - Characteristics (Phenotype)
Dominant: Dark hair, curly hair, dimples, tongue curling, detached earlobes, far-sightedness, double-jointedness, blood types A, B, rh+ blood.
Recessive: Blond hair, red hair, straight hair, attached earlobes, near-sightedness, cataracts, blood types O and rh- negative blood.
Heterozygous alleles = Bb.
The dominant allele determines the inherited trait.
Homozygous alleles = BB, or bb. The respective dominant or recessive trait is inherited.
Just because a trait is dominant does not mean it is common. Each colour represents different levels of light eyes (recessive trait).
- Blue area =80%+
- Green area =50-79%
- Olive area=20-49%
- Brown area=1-19%
- Black area=none.
- Explain epigenetics and how it bridges the gap between nature and nurture.
Epi-genetic = on top of; in addition to genetics
Refers to environmental factors that affect genes (by reducing, halting, or altering the expression of genes).
Can result in a phenotype that differs markedly from what would be predicted by its genotype.
Changes to your genome caused by the environment are propagated to the new generation (epigenetic inheritance).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4207041/ - look on slide at diagram too (Week 7)
Epigenetics: How does the environment alter gene expression? -
Environment does not change DNA-sequence (which typically remains constant throughout life).
However, the environment can trigger DNA – methylation.
A biochemical process that adds a methyl group (CH3) to the DNA molecule.
This changes the function of the affected gene by reducing or silencing its expression, and ultimately changes phenotype.
Nature and Nurture Interactions:
Examples of epigenetic modifications - Teratogens = harmful substances that can cause malformation or death of an embryo.
Thalidomite = medication to treat morning sickness during pregnancy, prescribed during the early 1960’s. Interfered with functioning of ‘growth genes’ during a sensitive period of limb development between weeks 4 – 6 weeks after conception, resulting in major limb deformities.
Examples of epigenetic modifications
Common environmental factors that were shown to cause DNA-methylation, including chronic exposure to:
Phenotypic alteration
Sunlight - risk of skin cancer
Tobacco smoke - risk of lung cancer
Alcohol consumption - addiction and various
diseases (organs, immune
system)
Use of hair-dye - potential risk of blood and bladder cancer
Asbestos (e.g. mould in homes) - risk of lung cancer
(Feli & Fraga, 2012)
What influences human development, heredity or environment?
Heredity AND environment interact in shaping human development.
Heredity and environment may not always contribute equally to our development, but one may take precedence over another at various times across the lifespan.
Interactions are bidirectional.
Can Nature and Nurture predict human development?
- E.g., does healthy biological (genetic) endowment, coupled with enriched social and physical environmental conditions predict ‘successful’ human development?
