Patterns of Development

• How does a fertilisied egg develop into a mature adult?

  Building blocks

  • Necessary input (genetic and environmental)

  Order and timing

  • developing systems need to build off existing ones
  • constraints
  • requires sequence of events in correct order and within certain time frame

  Critical periods

  • time periods in which specific experiences are necessary for typical development to occur

  Prioritise

  • Critical functions (i.e breathing, having heartbeat) emerge earlier than less critical skills (speaking, counting, reproducing)
• The human genome


  • 23 pairs of chromosomes
  • 22 pairs of autosomes
  • 1 pair of sex chromosomes = XY (male) XX (female)
  • Y chromosomes includes genes instructing development of testes
• Inputs (Genetic)


  Genes

  • Inherited
  • Made of DNA
  • Packed on 46 chromosomes
  • Genes → proteins → bodily functioning
  • Structural DNA sequence: directs the assembly of particular proteins
  • Regulatory DNA sequence: acts as ON/OFF switch
• Mitosis & Meiosis

  
• Gene transmission from parents to offspring

  Parent cells (2 x 23)

  Germline cells (1 x 23)

  Offspring (2 x 23)

  
• Gene transmission from parents to offspring

  • Which chromosomes within a homologous pair is transmitted to offspring is random
  • Result: 50% genetic information inherited from mother, 50% from father
  • Offspring genetic 'mixture' → source of genetic variation

  
• Crossing over


  During meiosis

  • Crossing over increases combination of gene variants offspring can inherit from each parent
  • Order of genes stays the same, but which gene variant is inherited from parent may vary
  • Result: infinite number of combination of gene variation

  
• Genetic variation


  Variation between gamates that parent can transmit to offpsring:

  • Segregation = only 1 of each pair of chromosomes transmitted
  • Independent asssortment = which 1 of the pair gets transmitted is random
  • Crossing-over between members of homologous pairs
• Genes on chromosomes


  • Genes organised along the chromosome; same order in homologous pairs
  • Different variants of genes: alleles

  
• Gene variants


  AA = normal skin

  Aa = normal skin

  aa = albinism

  • A = dominant allele
  • a = recessive allele
• Gene variation


  Offspring inherit allele from mum, one from dad

  Dominant versus recessive;

  homozygous versus heterozygous
• Genotype


  Unique combination of all alleles in individual
• Phenotype


  Observable trait (e.g., mum’s phenotype is blood type A; also e.g. ‘extraversion score’; ‘verbal ability’)

  • Phenotype = Genotype + environmental factors
• Inputs (Environmental)


  Prenatal

  • Hormones
  • Substances consumed by mother
  • Mother’s illnesses
  • Sound and light (late gestation)

  Postnatal

  • Alcohol/drugs
  • Environmental toxins
  • Infectious diseases
  • Parental love
  • Nutrition
• Gene/environment interactions


  Phenotype = Genotype + environmental factors