Topic 7 - Genetics, populations, evolution and ecosystems

• What is a phenotype?


  How an organism looks - their characteristics
• What is a genotype?


  the alleles an individual has for a certain characteristic
• What is homozygous?


  when two alleles of a gene are the same
• What is heterozygous?


  when two alleles of a gene are different
• What is evolution?


  Change in inherited characteristics of a population over time
• When does evolution happen?

  When natural selection occurs
• What is natural selection?

  nature selects characteristics which are best for the organisms survival rates due to survival of the fittest - these genes are then passed onto offspring
• Why is variation present?

  Due to random mutation
• What does diploid mean?

  has two sets of chromosomes
• What does haploid mean?

  has a single set of chromosomes
• What is the fixed location on an allele called?

  Locus
• What is F1 generation?


  first set of offspring of two parents
• When does monohybrid inheritance happen?


  When its heterozygous
• Why are the expected phenotypic ratios not always observed?

  • fertilisation/fusion of gametes is random
  • co-dominance
  • sex-linkage
  • samples taken from small populations ( not representative )
  • crossing over during meiosis
  • independent assortment of chromosomes
• What is co-dominance?


  When both alleles are dominant therefore they are both expressed in the phenotype
• why are most sex-linked genes found on the X chromosome?

  The Y chromosome is smaller than the X chromosome
• What is epistasis?


  Where an allele masks or suppresses the expression of genes at a different locus