According to the Chinese zodiac, 2012 is the Year of the Dragon. Dragons often appear in Chinese traditional beliefs as a large lizard, symbolising power, magic and prosperity. These creatures are also found in other cultures, from mythical European legends to spiritual Indian epics.
It is impossible to sequence and study the genome of such dragons, the obvious reason being, of course, because they are legendary creatures only found in storybooks but not in nature. However, assuming that the dragon is closely related to the lizard, we could only imagine what its genetic make-up would be like by looking at the first reptile genome made available.
Anolis carolinensis, or more commonly known as the green anole lizard, is the first non-avian reptile to have its genome sequenced. Amniotes, the first terrestrial vertebrates, diverged from other animals some 320 million years ago to form the mammalian and reptilian lineages, and reptiles further branched to lizards and birds. Results from the analysis of its genome, and the comparative analysis against birds and mammals, were published in August 2011. The results highlighted unusual features of the lizard genome, and revealed some extraordinary findings that could shed light on certain evolutionary mysteries.
Anoles are known to have good colour vision, including the ability to see in the ultraviolet range and to distinguish between similar colours and patterns. Anoles rely on colour vision to identify choice mates by recognising the vividly coloured flaps of skin beneath their necks. Thus, the family of genes that contributes to their excellent colour vision, known as opsins, is also responsible for their hyperdiversity.
In the anole lizard genome, scientists found an uncommon number of genes associated with colour vision. They uncovered 11 opsin genes that have no mammalian orthologues, yet all mammalian opsins have orthologues in anoles.
Using SynaSearch™, we can confirm the absence of an opsin gene in mammals and also examine the orthologues in other species. The pineal gland, or the ‘third eye’, of the lizard is used to detect irradiance and temperature. Mammals also have the pineal gland, but without the ability for photosensitivity. Therefore P-opsin (pineal gland-specific opsin) is expected to be absent in mammals.
From the SynaSearch™ results, it can be seen that anole P-opsin is highly similar to the opsin genes in chickens and frogs, besides other known lizards. To focus on the study of the evolution of reptiles, we can use SynaCompare™ and SynaTate™ to further compare the chicken and lizard P-opsin genes.