Nature vs Nurture:

  • genotypes - collection of genes responsible for various traits in an organism. 
  • genotypes make up phenotypes - observable characteristics of an organism. 
  • characteristics controlled by genotypes e.g. blood - controlled at a single locus. show discontinuous variation. fit into discrete groups.
  • characteristics controlled by environment e.g. height - controlled at many loci. show continuous variation. vary along a contiuem. 


  • polygenic - when several genes control the inheritance of a characteristic.
  • monohybrid - when inheritance is controlled by a single gene.
  • multifactoral conditions - when several genetic factors or more than one environmental factor is involved. 


  • determined by genes and environmental factors e.g. diet.
  • genotype influences - taller man have more children so genetic makeup changes over time, greater movements of people so less inbreeding.
  • environmental influences - better nutrition, improved health/sanitation, better vaccinations and antibiotics, better quality clothing, improved heating in houses, end of child labour. 

Hair Colour:

  • determined by genetics - amount of melanin. 
  • receptors for msh on surface of melanocyte cells. melanocytes place melanin into melanosomes to be transported to nearby skin and hair. they surround the nucleus to protect the dna from uv light damage. 
  • more receptors makes melanocytes more active - darker hair or skin.
  • uv light increases amount…


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