A. the dominant alleles are tall plant and axial flowers. When the offspring is dihybrid it means that it has both alleles for both characteristics, so the resulting phenotype reflects the dominant traits, or in other words, the dominant alleles. Because the offspring manifested all the tall and axial flowers features, the dominant alleles are tall plant and axial flowres.
B. If the offspring has all the same phenotype and is all dyhibrid, then their genotype is heterozygous for both characteristics, showing the traits that are dominant. The parents will then be homozygous for both of their characteristics - being one of them homozygous dominant for the tall plant allele and homozygous recessive for the terminal flowers allele, and the other homozygous recessive for the short plant allele and homozygous dominant for the axial flowers alllele.
C. The offspring proportions will result as: [tex] \frac{9}{16} [/tex] tall-axial, [tex] \frac{3}{16} [/tex] tall-terminal, [tex] \frac{3}{16} [/tex] short-axial, and [tex] \frac{1}{16} [/tex] short-terminal. You can do a Punnett square in which, on both sides of the F1 crossing, you have the following alleles' combination: tall-axial, tall-terminal, short-axial, and short-terminal. The resulting offspring should have these proportions.
