Describe how Seymour Benzer's phage experiments contributed to deciphering the genetic code

Seymour Benzer accidentally found a gene called r (rapid lysis) in the bacteriophage T4. The rll mutants were not able to grow on the bacterial strain in his experiment which became the catalyst for his discovery on the meaning of a gene. He collected rll mutants and mapped about 20,000 mutants and deletion. The finding of his study is that the rll gene could be represented by an estimate of 1,000 recombination units.