Which is a non-Mendelian trait? A. A trait controlled by many genes
B. A trait with a clearly dominant form
C. A trait controlled by one gene
D. A trait with two alleles

A non-Mendelian trait would be a trait that is controlled by many genes. The right option would be A.

Mendelian traits are traits that obey the principles of the Mendelian laws While non-Mendelian traits simply do not conform with the principles and laws of Mendel.

A trait that is Mendelian would have the following:

Thus, a trait that is controlled by many genes is clearly a non-Mendelian trait.

More on Mendelian traits can be found here: link

The answer would be A.

Explanation:

Non-Mendelian traits are traits that are not passed down with dominant and recessive alleles from one gene. Examples of polygenic traits are hair color and height. ... Other traits, such as blood type, show codominance, where there is no dominant or recessive allele.

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