Which characteristic is used to classify galaxies?

The galaxies were classified based on the shape and structure exhibited by them.

In the 1920's, the galaxies were classified based upon the shape and structure by famous scientist Edwin Hubble. He did it by a telescope with which he captured various galaxies existing. He ordered (or "arranged") their shapes as winding, banned winding, curved, sporadic, and impossible to miss. This framework was known as the Hubble morphological succession of cosmic system types.  

Hubble noticed that a few universes, similar to the M31-Andromeda Galaxy, showed up as circles and had arms of stars and residue which showed up in a winding example. Like M31, these worlds showed up almost uniform in splendor. Likewise, Hubble saw that in a portion of these sorts of worlds the arms were all the more firmly twisted around the cosmic system. He called these winding systems. Our Galaxy, the Milky Way, is a case of a winding universe.  

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

answers are:

lysogenic     viral dna merges with host cell dna

lysogenic     no symptoms

lytic               viral dna takes over

lysogenic     virus does not destroy host cell

lytic               virus destroys host cell

lytic               induces symptoms of viral infection

lysogenic       cell reproduces and spreads provirus