Question

question 7
which of the following might explain how two separate genes control a single trait?
one gene functions better at higher temperatures.
two genes cannot control a single trait.
both genes have the same alleles.
there are two genes to control two separate steps in a pathway.

Explanation:

Genes can control traits through biochemical pathways. If a trait is the result of a multi - step pathway, each step can be controlled by a different gene. For example, in pigment synthesis, one gene may code for an enzyme that converts precursor A to intermediate B, and another gene may code for an enzyme that converts intermediate B to the final pigment (trait). Temperature - related gene function (first option) is about gene expression variation with temperature, not two - gene control of a single trait. Two genes can control a single trait (contradicts the second option). Having the same alleles (third option) doesn't explain two - gene control of a trait; alleles are variants of a single gene.

Answer:

There are two genes to control two separate steps in a pathway.