With independent assortment, the ratio of phenotypes in the f2 generation of a cross between true-breeding strains (aa bb x aa bb) can be described as 9: 3: 3: 1 when a and b are dominant over a and b. to what phenotype does the "9" in the ratio refer?

a. recessive for both traits
b. dominant for one trait and recessive for the other
c. dominant for the a trait and recessive for the b trait
d. dominant for both traits

B. Dominant for one trait and recessive for the other

Explanation:

using the Punnetts square for the question above, the 9 in the ration refers to a dominant for both traits such as AABB, AaBb.

while the 3: 3 refers to a dominant for a single trait and recessive for one such as AAbb, Aabb, aaBB, aaBb

and the 1 refers to recessive for both traits such as aabb.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation: