Mutations and rearrangements that occur by misalignment during DNA replication are frequent sources of genetic variation in bacteria. Dislocations between a replicating strand and its template at repetitive DNA sequences underlie the mechanism of these genetic events.
Cnidarians take on two basic forms, a medusa and a polyp. The medusa form is a free-swimming structure which consists of an umbrella-shaped body (called a bell), a fringe of tentacles that hang from the edge of the bell, a mouth opening located on the underside of the bell, and a gastrovascular cavity. The mesoglea layer of the medusa body wall is thick and jelly-like.
Cnidaria is one of the more primitive animal phyla. It includes aquatic organisms such as jellyfish, sea anemones, corals, and hydras. Most cnidarians are marine, although a few, such as the well-known hydra, are freshwater species.nidaria A phylum that comprises the sea anemones, jellyfish, and corals, and which is known from the late Precambrian. Cnidarians are basically radially symmetrical and have tentacles. The body contains a gastrovascular cavity and the body wall is diploblastic.