Figure 1. Picture of the four chromosomes from a wild type Drosophila female (top left), and XXY female (top right). Shown below is a mechanism for ‘crossing-over’, which explains the origins of the extra chromosome found in the XXY female. The drawings are based on Bridges (1916).

Figure 2. Genome atlas for phiX174. The outer three lanes correspond to DNA structural properties (curvature, stacking energy and nucleosomal ‘position preference’). All the genes go in the same direction (clockwise), and hence are annotated as blue. Two different types of inverted repeats are indicated in the next two lanes, followed by GC skew and the inner-most circle is the relative AT content (red being more AT rich, and blue represents GC rich). Hansen Permissions.

Figure 3. Restriction map (left), and gene map (right) for the bacteriophage phiX174. Note that the genes are all in the same orientation, as indicated by the green arrows. The red lines represent different mapped transcripts. These figures were kindly provided by Flemming Hansen.

Figure 4. Genome atlas for the bacterial genome of Bradyrhizobium japonicum, strain USDA 110. The lanes are similar to those in the atlas in Figure 2, except the repeats are now global direct and inverted repeats, which represent regions of at least 100 bp with homology either on the same strand (direct repeats), or on the opposite strand (inverted repeats). As is characteristic for many bacterial genomes, the overall level of repeats is quite low, with less than 5% of the genome containing repeats with more than 80% homology.