Answer:
a) There are eight expected phenotypes from the cross F1 x F1:
1) Tall, green pods, purple terminal flower
2) Tall, green pods, white axial flower
3) Tall, yellow pods, purple terminal flower
4) Tall, yellow pods, white axial flower
5) Dwarf, green pods, purple terminal flower
6) Dwarf, green pods, white axial flower
7) Dwarf, yellow pods, purple terminal flower
8) Dwarf, yellow pods, white axial flowers
b) If you cross the triple heterozygous for this characteristics with the parental dwarf pure stain, it is expected to obtain each of the phenotypes listed above, with the same probability
Explanation:
a) If we analyze the given data, we see that from the cross of a plant that is tall, has green pods and purple terminal flowers with one that is dwarf, has yellow pods and white axial flowers, all the progeny is tall, has green pods and purple terminal flowers.
This means that these three genes exhibit total dominance, being the dominant alleles tall (D), green pods (Y) and purple terminal flowers (W). While the recessive alleles are Dwarf (d), yellow pods (y) and white axial flowers (w).
As a result of the parental crossing, all the F1 individuals have the phenotype tall, green pods and purple terminal flowers and the genotype DdYyWw.
If we cross individuals from F1, F2 individuals can exhibit eight possible phenotypes (listed above) that arise from the combination of the alleles of the three genes considered. To see the possible sixty four genotypes, you can check the attached figure with the Punnett square F1 x F1, made considering the eight possible gametes that members of F1 can produce (DYW, DYw, DyW, Dyw, dYW, dYw, dyW, dyw).
b) By crossing one F1 individual with a dwarf parent, we're crossing the genotypes DdYyWw x ddyyww, a triple heterozygous with a parent that is triple recessive homozygous. This is known as backcrossing and by doing that we're combining all the eight possible gametes from F1 with the only gamete produced by the parental strain (dyw). As a result, we get all the eight possible phenotypes, each with the same probability, as there are only eight possible genotypes from this crossing, each one corresponding to a different phenotype (see the Punnett square F1 x "Parental Dwarf" )
