A zoo blot (Fig. 1) is the result of an experiment in which a short DNA fragment from the genomic region of interest is first cloned and then used as a radioactive probe to test for related DNA from a variety of species by Southern blot analysis. If hybridized fragments related to the probe are found in several species, there is a strong possibility that the probe is an exon of a gene, because of its sequence conservation (1). Such candidates can be further characterized by DNA sequencing to determine whether they contain open reading frames (ORFs). If so, the identification of the new protein-coding gene is possible by further experiments, such as isolation of complementary DNA or messenger RNA. Thus, a zoo blot is a powerful tool, not only to see how the probe of interest is conserved among a variety of species, but also to identify a new protein-coding gene.
Figure 1. Schematic representation of a zoo blot. Southern blot analysis of genomic DNAs from various species was performed using a particular probe, such as a segment of human DNA.
