6.2.3

• dihybrid - involving two gene loci
• The simultaneous inheritance of two characteristics

  investigations that examine the simultaneous inheritance of two characteristics are dihybrid crosses

  • in one dihybrid cross, Mendel examined the inheritance of seed shape + seed colour in pea plants

  → he crossed true-breeding pea plants with yellow + round seeds with true-breeding pea plants that had green + wrinkled seeds

  • all the F1 generation were hybrids, having the phenotype of yellow + round seeds

  → each plant in the F1 generation is heterozygous for both genes (seed colour + shape); therefore yellow + round are both dominant trait

  
• from the results of his dihybrid cross, Mendel deduced that:

  • the alleles of the two genes are inherited independently of each other, so each gamete has one allele for each gene locus
  • during fertilisation, any one of an allele pair can combine with any one of another allele pair