| Comments |
P.266 4th paragraph: "Different proteins can be specified by overlapping transcription units.
Overlapping genes and genes-within-genes: Simple genomes have high gene densities (roughly one per 0.5, 1, and 2 kb for the genomes of human mitochondria, Escherichia coli, and Saccharomyces cerevisiae, respectively) and often show examples of partly overlapping genes. Different reading frames may be used, sometimes from the same sense strand. In complex organisms, such as humans, genes are much bigger, and there is less clustering of protein-coding sequences (Table 9.5)." P.271 bottom paragraph: "Processed pseudogenes are defective copies of a gene that contain only exonic sequences and lack an intronic sequence or upstream promoter sequences. They arise by retrotransposition: cellular reverse transcriptases can use processed gene transcripts such as mRNA to make cDNA that can then integrate into chromosomal DNA (Figure 9.12). Processed pseudogenes are common in interspersed gene families (see Table 9.5)." |