genetic diagrams

• An allele is an alternative form of the same gene.
• genetic variation

  • Achieved during metaphase of meiosis 1 through independent assortment of chromosomes.
  • Achieved during metaphase of meiosis 1 through crossing over.
  • Achieved during DNA replication through random mutation.
  • Achieved during fertilisation because different gametes have different genomes.
• • Dominant allele = The allele that is always expressed in the phenotype (the stronger one)
  • Recessive allele = Is only expressed if there isn’t a dominant allele present
• Dihybrid crosses are those where we consider the inheritance of two characteristics at the same time.
• typical ratio for a dihybrid cross =

  9 : 3 : 3 : 1