Many genes specify traits by encoding proteins. The first person to suggest the existence of a relation between genotype and proteins was the English physician Archibald Garrod. In 1908, Garrod correctly proposed that genes encode enzymes, but, unfortunately, his proposal made little impression on his contemporaries. Later, George Beadle and Edward Tatum examined the genetic basis of biochemical pathways in the bread mold Neurospora and developed the one-gene, one-enzyme hypothesis, which suggested that genes function by encoding enzymes and that each gene encodes a separate enzyme. Later research findings showed that some proteins are composed of more than one polypeptide chain and that different polypeptide chains are encoded by separate genes, so this model was modified to become the one-gene, one-polypeptide hypothesis.