Monohybrid and Dihybrid cross

• Monohybrids are used to show which trait is dominant and recessive.
• A test cross is used in genetics to determine which trait is dominant and recessive.
• Co-dominance both alleles of a gene are equally dominant and expressed in the phenotype
• Incomplete dominance neither one of the two alleles is dominant over the other resulting in an intermediate form occurring in the phenotype
• Complete dominance is when one allele masks the other in the phenotype
• Dihybrid crosses contain two sets of alleles
• The ratio of 9:3:3:1 is produced in a dihybrid when crossing two heterozygous parents.
• Heterozygous means that an organism has one dominant and one recessive allele
• Homozygous recessive means that an organism has two recessive alleles.
• Homozygous dominant means an organism has two dominant alleles.
• A ratio of 3:1 or 75\25% occurs when you cross two heterozygous parents.
• A ratio of 1:1 or 50/50% occurs when you cross a heterozygous parent with a homozygous recessive parent.