phenotypes and variation

• phenotypes

  • observable characteristics of an organism
  • changes due to genetic factors or environmental factors
  • phenotype= genotype+environment
• monogenetic=single gene controlling characterstics- discontinuous variation eg blood group

  polygenetic=several genes controlling characterstics-continuous variation eg height
• environmental factors- effect of phenotype

  • length of sunlight hours
  • supply of nutrients
  • availability of water
  • temp range
  • oxygen levels
• discontinuous variation

  • qualitative difference in phenotypes of pop gives rise to discontinuous
  • fall into discrete/distinguishable categories-cant fall between
  • eg blood group
• continuous variation

  • quantitative difference in phenotype
  • do not fall into discrete categories
  • a range of values exist between 2 extremes eg mass or height
  • lack of categories and presence of a range
• causes of continuous variation

  • some phenotypes affected by multiple diff genes or multiple alles at many diff loci