By comparison most genes of higher eukaryotes are

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Unformatted text preview: ns). By comparison, most genes of higher eukaryotes are composed of large numbers of noncontiguous coding regions (exons) separated by introns, sometimes hundreds of them. The low frequency of introns in yeast may be related to a similarly low frequency of “processed” pseudogenes, which, like introns, are common in higher eukaryotes. Pseudogenes, we have seen, contain coding sequences that resemble those of real genes, but because the pseudogenes lack introns and transcriptional promoters, the coding sequences are not expressed. Figure A.5 Analysis of open reading frames in the yeast genome. The total number of ORFs of the indicated length encoded in the S. cerevisiae genome are shown in red. The total number of annotated ORFs in the Saccharomyces Genome Database (SGD) are shown in green. The scale for the total number of ORFs is compressed 10-fold relative to the number of annotated ORFs. The difference in magnitude is therefore underepresented by 100-fold. The black vertical line indicates the 100-amino-acid cutoff chosen for annotating t...
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