At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genome of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for most of the rest?

Select one:
a. non-protein-coding DNA that is transcribed into several kinds of small RNAs without biological function
b. DNA that is translated directly without being transcribed
c. non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
d. "junk" DNA that serves no possible purpose
e. rRNA and tRNA coding sequences