The yeast genome was sequenced more than 10 years ago, yet the total number of genes continues to be refined. The sequencing of closely related yeast species was important for validating the identity of short (less than 100 nucleotides long) open reading frames (ORFs) that were otherwise difficult to predict. What is the main reason that these short ORFs are hard to find?
(a) The human genome does not have short ORFs.
(b) The short ORFs code for RNAs.
(c) Many short stretches of DNA may, by random chance, not have a stop codon, making it difficult to distinguish those that code for proteins from those that do not.
(d) Short ORFs occur mainly in gene-rich regions, making them difficult to identify by computer programs.