Recent research has identified two genes that determine height in humans. individuals with the "tall" allele for both genes are taller than those with the tall allele for only one. individuals with one tall allele, in turn, are taller than people who do not have the tall allele for either gene. this is known

Additive effect.

Explanation:

Additive effect may be defined as the phenomena in which two or more genes contribute for the single phenotype pf the organism. The additive effect do not follow the Mendel's law and shows quantitative trait.

The gene that are responsible for height shows different effect. The tall allele with two genes has more height than the single tall gene. Each gene has its effect and the addition of the particular gene enhances the phenotype effect of that particular gene. Here, the tall shows the additive effect.

Thus, the answer is additive effect.

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