Final answer:
Prior to the year 2000, our understanding of gene interplay was built on the work of early geneticists like Mendel and researchers who identified DNA as the genetic material, leading to the human genome project.
Step-by-step explanation:
Up until the year 2000, most of what was known about the interplay of genes came from foundational research by scientists studying heredity, gene function, and the structure of DNA. Early genetic discoveries were made by researchers like Gregor Mendel, who, in the 19th century, analyzed pea plants to establish the basic principles of heredity.
Building off Mendel's work, the "one gene-one enzyme" hypothesis by George Beadle and Edward Tatum, the transformation experiments by Frederick Griffith, and the identification of DNA as the genetic material by Oswald Avery and his colleagues, further advanced our understanding of genetics. Finally, the work of Alfred Hershey and Martha Chase validated DNA as the molecule responsible for storing genetic information. These scientific endeavors paved the way for the eventual mapping of the human genome, which promised new insights into gene function and the development of more specific pharmaceuticals.