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.
The Cnidarians include the hydroids, jellyfish, anemones, and corals. All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name Cnidarian literally means stinging creature..The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger.n fact, the phylum name Cnidarian literally means stinging creature.. The stinging cells are called cnidocytes and contain a structure called a nematocyst. The nematocyst is a coiled thread-like stinger.