The existence of the gene established by which of the following?
a. george beadle
b. edward tatum
c. gregor mendl
d. wilhelm johannsen
e. james watson

Wilhelm Johannsen.

Explanation:

Gene may be defined as the functional segment of DNA that are heritable in nature. Genes are responsible for the formation of protein product and observable characteristics of the organisms.

The Danish botanist, Wilhelm Johannsen coined the term gene. He explained the existence of the gene by the pure line experiments of the genetics. The term gene was established in opposite to the panegenes.

Thus, the correct answer is option (d).

i think the answer is b.