Diversity + Natural Selection

• Describe crossing over and how it increases genetic diversity (4)

  1. Homologous pair form a bivalent
  2. forms chiasma
  3. allows for alleles to be exchanged
  4. so that new combinations can be produced, inceasing variation
• Explain the role of independent segregation in meiosis (2)

  1. to provide genetic variation
  2. by allowing for different combinations of maternal and paternal alleles/chromosomes
• Natural Selection

  • within a population there is genetic variation
  • this is caused by random mutation
  • This may result in the creation of new alleles
  • if selection pressure mean the new allele is advantageous
  • those with the new allele will survive, reproduce and pass the allele onto their offspring
  • over several generations, there will be an increase in the allele frequency
• Define gene mutation and explain how it can have No effect and a Positive effect

  1. change in base sequence
  2. formation of new allele
  3. genetic code is degenerate OR mutation is in an intron
  4. does change AA but no effect on the tertiary structure
  5. new allele is recessive so no influence on phenotype
  6. may result in reproductive success OR may result in increased survival chances