Final answer:
The phenotypic ratio of a cross between two sea stars heterozygous for both color (orange or yellow) and tube feet length (long or short) is typically 9:3:3:1, assuming complete dominance and that each trait is inherited independently.
Step-by-step explanation:
The question concerns a cross between two sea stars that are both heterozygous for two traits: orange or yellow color and long or short tube feet. In genetics, such a cross is known as a dihybrid cross because it involves two different traits. Using the principles of Mendelian genetics, we can predict the phenotypic ratio of the offspring from such a cross.
Each trait is inherited independently, and because each parent is heterozygous for both traits (BbTt), we use a Punnett square to determine the possible gametes and offspring phenotypes. The phenotypic ratio for a dihybrid cross between two heterozygous parents (BbTt x BbTt) is typically 9:3:3:1. However, in this case, the question has not provided the dominance relationships between the alleles, so it is not possible to determine the exact phenotypic ratio without additional information. If we assume complete dominance where 'B' is dominant over 'b' (orange over yellow) and 'T' is dominant over 't' (long over short), we would expect 9 orange with long tube feet, 3 orange with short tube feet, 3 yellow with long tube feet, and 1 yellow with short tube feet, which corresponds to a 9:3:3:1 ratio.