Richard John Roberts (1943 - present) was awarded half of the 1993 Nobel Prize in Physiology or Medicine for his discovery of introns – sections of DNA spliced out afer transcription -- in eukaryotic DNA and the mechanism of gene splicing. Roberts established that adenovirus genes are discontinuous and that the segments of DNA that code for proteins are interrupted by lengthy stretches of noncoding DNA called introns. Roberts made this discovery independent of fellow Nobel Laureate Phillip A. Sharp. Up until Roberts and Sharp discovered introns and exons (the coding part of DNA), biologists believed that genes consisted of unbroken stretches of DNA, all of which encoded proteins.